Is this a reasonable 2 week itinerary?

Here's what it looks like to me from your itinerary. Is this correct?

June 10: Arrive Amsterdam, sleep in Amsterdam (3 nights)
June 13: Leave for Cologne, sleep in Cologne (1 night)
June 14: leave on Bike and Barge tour to Mainz, Sleep on boat?
June 21: Arrive Mainz. sleep in Mainz (1 night)
June 22: Leave for Nuremberg, sleep in Nuremberg (1 night)
June 23: Leave for Munich, sleep in Munich (1 night)
June 24: Fly back to Minneapolis from Munich

If so, you are jumping around a lot. That may be fine for you and may be your style, but you're spending so much time traveling that you won't have a whole lot of time to actually see the places you are traveling to.

Amsterdam looks fine; even Cologne. But you are only giving Nuremberg one night, which won't be even a whole day of sightseeing. I would suggest either eliminating Nuremberg and spending that extra time in Munich, or eliminating Munich (except for the airport) and spend that extra time in Nuremberg. Or possibly eliminating the overnight in Mainz and taking the train from Mainz directly to Nuremberg, where you could spend an extra night, and then keep that schedule for Munich as is.

June 14: leave on Bike and Barge tour to Mainz, Sleep on boat?

I would think that the tour company would tell you where you will be sleeping - or that you must make your own arrangements.

I think it's a GREAT idea to get in on the Johannisnacht celebration.

What Mardee says about the itinerary from the 21'st onward is on point. Is your flight out of MUC in the pm of the 24th already set in stone? Assuming the answer is YES, then I'd suggest this...

June 21-23 (2 nights) in MAINZ. (Please forgive Rick and his writing staff for the minor sin of not covering Mainz, they know not what they do!) You need to make a little time here for some good historical stuff....

Gutenberg Museum (open Sat 6/21 and Sunday 6/22) 1000+ reviews, 4.5 stars on Tripadvisor.
Temple of Isis and Mater Magna (open Sat 6/21 'til 18:00.)
Other Mainz Museums
Mainzer Dom
Stephanskirche

June 23-24 (one night) in Nuremberg Leave Mainz early to maximize time in Nuremberg; there's a direct ICE train (7:40 - 10:27.) Drop bags. See what you had in mind.

June 24: Not clear what time the flight will be... but use whatever morning time you might have for Nuremberg. There are direct RE trains from Nuremberg to MUC airport. 8:07 - 10:41, 10:11 - 12:41, 12:11 - 14:41. I would make a point of avoiding any journeys that require a connection, something you cannot afford to miss on the day of your flight.

Not sure if you have bought your tickets but if your focus is Germany, both Lufthansa and Condor fly there nonstop from MSP.

You are probably proposing a Delta itinerary and then it’s easy to fly back from Nuremberg, a KLM flight to AMS or Air France flight to Paris will connect onward to MSP. This way you avoid the trek to Munich entirely. Checking flights for your dates using Delta’s flight MUC>>DTW is $200 cheaper than flying out of Nuremberg so there’s that.

Thanks. I appreciate the input. Only bike and barge was bought so far (sleep on boat). Writing out the itinerary and hearing feedback makes me realize we need to scale back traveling and explore areas deeper. The seven nights between Cologne and Mainz will be daily bike trips exploring the area. I think we will add a few nights in Cologne before we leave and a few nights in Mainz/nearby cities after the tour and call it done.

Has anyone tried flying to Reykjavik round trip ($509!) and then flew to/from German cities as a thrifty option?

Icelandair is a solid MSP choice, into Frankfurt, Berlin or Munich, mix and match. Icelandair at $500 is a steal, that fare won’t last. Note it will be only single aisle planes, and food and alcohol extra (free items on Delta and wide body jets).

I fly round trip Icelandair from Frankfurt to the US all the time. It is my preferred way of getting there. I also prefer the smaller, 1 aisle planes. You board and deplane so much faster!
If they are flying to a city you like in Germany, at a good price, go for it.

Realizing now you are talking separate tickets changing planes in Reykjavik. Icelandair is no longer offering that fare but Delta is (for now). You would not be able to synch these Delta times with Europe flights without spending the night (at least on the return, the Delta flight returns to MSP in the morning before flights from Europe arrive in Iceland. Unless you plan to sleep at the airport you will likely eat up the savings of 2 tickets dinking around with expensive hotels. And there’s nothing much around the KEF airport.

"The seven nights between Cologne and Mainz will be daily bike trips exploring the area. I think we will add a few nights in Cologne before we leave and a few nights in Mainz/nearby cities after the tour and call it done."

It sounds like you intend to add roughly a week altogether to the bike-tour week. Cologne and Mainz might be good for some of that time. But there are other worthwhile neighbor-towns left and right of the Rhine River which you should consider as additions or alternatives, places that are easy to get to thanks to the extensive train system.

What about Trier, Germany's oldest city, in the Mosel River Valley?
https://historicgermany.travel/historic-germany/trier/
https://www.trier-info.de/en/places-of-interest

Numerous other Mosel River towns make for good exploring as well:
https://www.mosel-inside.de/en/travel-guide/mosel-villages.html

Burg Eltz Castle is in the hills north of the Mosel River; you can hike there from Moselkern or take a short bus ride:
https://mostlytraveled.wordpress.com/2022/05/10/day-15-burg-eltz-castle/

Limburg, in the Lahn River Valley, is a half-timbered old-world gem.
https://www.tripadvisor.in/Attractions-g198491-Activities-oa0-Limburg_Hesse.html

In Bad Sobernheim there's an "open-air" museum with dozens of historic buildings detailing life in this part of rural Germany over the previous 500 years or so.

https://www.freilichtmuseum-rlp.de/english/english/

What isn't clear is where the bike tours will take you and what places you will explore in between Mainz and Cologne. Knowing this might help us provide more focused tips.

Thanks everyone!

Here is our 7 night itinerary on the boat/bike tour:
Day 1: Arrival to Cologne
Embarkation at 04:00 pm. Enjoy the evening on board or with a Kölsch beer in one of the pubs with a view over the river Rhine.
Day 2: Cologne – Bonn, Cycle tour, approx. 37 km. Before starting your first cycle tour, take the opportunity to stroll through the Old Town. Afterwards you start your cycling tour to the city of Beethoven, Bonn. This federal city and former capital of Germany still has international flair. Visit the leisure island Groov amidst a vast landscape of the Rheinaue wetland in the Cologne suburb Porz-Zündorf. In Bonn there are museums like the House of History or the Bundeskunsthalle courting for visitors’ attention and the House of Beethoven, the Rheinaue as well as the Bundesviertel with the path of Democracy are equally worth a visit.
Day 3: Bonn – Andernach, Cycle tour, approx. 45 km You will continue towards Andernach by bike today. Königswinter with its castle Drachenburg on the Drachenfels (steep ascent) as well as the Sea Life with aquariums. Your destination for today, Andernach, is famous for the world´s biggest cold water gush spring with its impressive fountain of 60 meter.
Day 4: Andernach – Koblenz, Cycle tour, approx. 25 km. On your way to Koblenz you will find castle Engers in Neuwied. At the famous “Deutsche Eck” (german corner) the river Mosel merges with the river Rhine. Another place of interest is the fortress Ehrenbreitstein which you can also reach by cableway across the Rhine in Koblenz. Tickets for the cableway are available on board.
Day 5: Koblenz – St. Goar/St. Goarshausen, Cycle Tour approx. 38 km. You continue your journey by bike up the river Rhine through the UNESCO world heritage site Upper Middle Rhine Valley. You will pass the romantic fortress Marksburg, the only hilltop castle of middle Rhine which has never been destroyed, as well
as the city Boppard with its fortress Kurfürstliche Burg, before you will reach St. Goar. Here you will find the ruins of fortress
Rheinfels, which is the biggest of its kind along the Rhine. The fortresses Katz und Maus (cat and mouse) in St. Goarshausen on the other side of the Rhine are also worth visiting.
Day 6: St. Goar/St. Goarshausen – Rüdesheim, Cycle Tour approx. 32 km. Again you will pass very beautiful Rhine castles like Burg Reichenstein and Burg Rheinstein. You will cycle past the famous rock Loreley before you reach Rüdesheim. In Rüdesheim we recommend a city walk around the historical town with its beautiful half-timbered houses. Or treat yourself to a ride on the cable car up to the Niederwald monument. Here you will have a beautiful view over the old town of Rüdesheim and the river.
Day 7: Rüdesheim – Mainz, Cycle Tour approx. 32 km. On your final cycling stage you will find the Rhine at its best. The city Eltville am Rhein with its emblem, the castle Kurfürstliche
Burg, is on your way. Mainz, your destination of today, presents itself with numerous impressive buildings. You may want to visit its cathedral Hoher Dom St. Martin, one of the proud imperial cathedrals of Germany, or the castle Kurfürstliches Schloss. In the old town, go to Augustinerstraße and the Kirschgarten with its lovely timber framed houses and wine restaurants.
8. Tag: Departure from Mainz
Disembarkation after breakfast until 9:00am.

Whew! Good suggestion to inspect our current itinerary a little closer as this may tire us out!

I am excited to find a $573 fare round trip to Amsterdam for the dates we are going, train to Cologne, flying from Nuremberg to Ams at the end of our tour.

I've heard many great suggestions on this forum about where to visit. So far I think we'll do three nights in Amsterdam, one night in Cologne, seven nights on the boat, One night in Mainz, one night in Nuremberg.

Is this too much? We are married couple in our '50s. Only European trip was our honeymoon 20 years ago and that was five nights.

If you've got 5 extra nights beyond the 7 on the boat, and you are allocating them 3-1-1 in the cities you named, then there is no time for anything else (such as the Mosel River, Burg Eltz, or other places I posted in my most recent post.) There is also very little time for Mainz or Nuremberg.

You begin "Tag 8" at 9:00 am as you step off the boat. I am guessing you did not see all that much of Mainz on the afternoon prior. So you can move on from there right away, or if you wish to park your bags at the station and spend a few hours on the sights you might have missed, or on Johannisfest, that seems a good option.

Whether you linger in Mainz or you move on right away, I suggest returning as you came by train in the direction of Amsterdam to a Rhine base town for "Nacht 8 & Nacht 9." There are some things you have missed. The business of traveling to Nuremberg for one night and then flying from Nuremberg to Amsterdam would be folly, IMHO.

"The fortresses Katz und Maus (cat and mouse) in St. Goarshausen on the other side of the Rhine are also worth visiting."

Sorry, this bit is nonsense. There is no public access to either of these castles.

"You will pass the romantic fortess Marksburg, the only hilltop castle of middle Rhine which has never been destroyed"

Because your bike journey south along the Rhine appears to follow the river on the Boppard/St Goar side, you will only be viewing Marksburg from the opposite river bank. And if there is one must-see / must-tour castle on the Rhine River, it is indeed Marksburg, just south of Koblenz in Braubach.

https://www.deutschland-luftaufnahmen.de/wp-content/uploads/2020/10/Marksburg.jpg
https://www.marksburg.de/en/circuit/#/

So my suggestion for Tag 8 (presumably Sa June 21) is to catch one of the direct northbound trains from Mainz to BOPPARD for 2 nights there. From Boppard there are multiple ways of getting to Braubach, where Marksburg is located. And Boppard is just a good place to stay... many hotel and restaurant choices, some right on the waterfront promenade.

Arrival at Boppard at 11-12:00? Drop bags at hotel, see town, take the chairlift ride and the walking path at the top to Gedeonseck Terrace for a terrific view of the river valley.

Arrival at Boppard late in the day? See what you can and find dinner.

Tag 9, June 22: See town and do the chairlift if you didn't already, then head to Braubach/Marksburg in the afternoon. Done with Boppard already? You might want to catch a train to Remagen (NW of Koblenz) for the WW II museum there...

https://bruecke-remagen.de/?setlang=en

Then train to Braubach for Marksburg in the afternoon, then back to Boppard.

Braubach, btw, is a very attractive old-world town worth a walk-through and/or a meal:

https://farm5.staticflickr.com/4143/4751924826_98980aa49f_o.jpg

You should be able to find Boppard, Braubach, Remagen and Koblenz on the railway schematic below:

https://www.vrminfo.de/fileadmin/data_vrminfo/PDF/Gaesteticket/Infoflyer_Gaesteticket_englisch_2022.pdfSCj

At the end of all this, catch a train from Boppard to Schiphol airport on the 23rd (roughly 5.5 hours.)

If you cycle at all at home, the cycling shouldn’t tire you out. 30+ km over flat roads is pretty mild