Train - Quer-durch-land-tkt

Two caveats with the Quer-durchs-Land-Ticket. 1, you can only use it for regional trains, not the fast ICE or IC trains, and, 2, you can only use it after 9 AM on work days. Even though it takes a lot longer, I would want to take the regional train route down the Rhein river, through the gorge with it's castles and vinyards, so using the AdLT would not matter for me. And I usually don't like to start traveling before 9 AM.

If you purchase a QdLT online from the Bahn website, it will come date stamped and you can only use it on that date. But the ticket can be purchased right up until train time for the same price (from an automat), so if you aren't absolutely sure of your plans, or don't mind spending a minute or two in the station buying your ticket, wait until you get there. You can buy it from an automat the day before, but it will prompt you for the date and make sure you enter the date on which you want to use it.

do you just purchase this on the Bahn website and that is all we will
need to get on the train?

With ticket, either purchased from the Bahn website or at the station, in hand, you just get on the train. However, to prevent you from selling it to someone else when you are through with it, you must print your name(s) on the space provided on the ticket before boarding.

Just a follow-up to Lee's notes on the QDLT:

"..you can only use it after 9 AM on work days."

There's also the Happy Weekend Ticket for Sat or Sun with no hours restrictions. But you've likely matched the QDLT to a weekday outing already.

"I would want to take the regional train route down the Rhein river..."

You'd be starting AND ending your final day in Mainz/Wiesbaden, correct? If so, it's a round trip, which will indeed mean a lot of hours on the train. There are different kinds of regional trains. If you can find an RE-only (regional express) connection, you'll save a little time over the "milk-run" trains that stop in every town. That's only from Mainz... From Wiesbaden you're stuck with at least 1 milk-run train for the 2-train journey to Cologne.

I wonder where you'll be on the next-to-the-next-to-last night? Maybe that night could be spent in Cologne, or maybe you could travel to Cologne on the morning of the next-to-last day from some closer location than Mainz.

Of course there are shorter trips you could make to see some nice churches. Mainz has some as well. And you mentioned "a few other sites" - did you mean in Cologne, or elsewhere along the way? Rheinfels Castle and Marksburg Castle would both be a lot closer than Cologne. Let us know your interests if you need some suggestions if Cologne seems to far.

We will be doing a Rhine River Cruise (from Boppard to St Goar) before heading to either Mainz or Wiesbaden (tour company has not made final hotel stay). Would Burg Elitz Castle be doable from Mainz or Wiesbaden instead of Cologne? I know the Cologne train will take approx 5 hours round trip but also wanted to see if I could do the train and the planning by myself for a future visit to Germany (trial run). Thank you.

First place, never do a Rhein cruise upriver (to the SE, eg, Boppard to St. Goar), against the current. The trip in that direction is excruciatingly slow, about 50% longer timewise than down the river.

Second, the section of the Rhein between Bacharach and St. Goar is the most interesting. Make sure you include it. Do Bingen to St. Goar, or Bacharach to Boppard, or, if you want to use the time for other things, just Bacharach to St. Goar.

"Would Burg Elitz Castle be doable from Mainz or Wiesbaden instead of Cologne?"

From Mainz it's 4 hours round trip by train (with a change of train in Koblenz in each direction) just to Moselkern and back using the regional trains and one of the inexpensive day passes. Then you'd have to add in an hour's walk to the castle and about the same coming back to Moselkern. So 6 hours in transit for a 1-hour castle tour. Your call.

In my previous post I suggested Rheinfels Castle. That would require only 2 hours of total transit time by direct train from Mainz to St. Goar, plus a relatively short uphill walk from town, or possibly a ride with the castle-shuttle. Rheinfels has a museum and the tour is self-guided. There is also a nice indoor/outdoor cafe at the adjacent hotel with a nice view. St. Goar itself is a nice town with a few tourist diversions including a cuckoo clock shop and a beer stein shop. They are located on the Heerstrasse, a pedestrians-only street lined with cafes and a bakery or two. Try Alla Fontana for Italian food - it's on a side street that joins Heerstrasse.

Because this train outing is shorter, you might have time to stop over in Bacharach on the way back to Mainz for 1-2 hours. It's a small, delightful old-world town with many half-timbered buildings.

Cruise: Boppard to St. Goar is less scenic than other parts and as Lee points out, it's in the wrong direction. With that same 1 hr and 20 minutes, you could instead see the BEST part of the Rhine - Bingen to St. Goar, as shown on this cruise company map. Just take the train to Bingen instead of Boppard to start the cruise. (While it's possible to cruise from St. Goar to Bingen instead, that would take 2 hrs. 40 min's. - twice as long.) Once you leave the boat in St. Goar, catch the train to Mainz (1 hr.)

It occurs to me that if you need to be in a real city at the end, it might be wise to make KOBLENZ your final hotel town. Koblenz is a major train hub and would provide quicker train access to Burg Eltz or to the outstanding Marksburg Castle which is in the charming town of BRAUBACH, only 10 minutes from Koblenz by train, and also to Boppard and St. Goar. Direct RE trains from Koblenz to FRA airport terminal take 1 hr. 30 minutes and typically depart hourly in the morning hours starting around 5 am.