8 days, two locations

"She like cities and museums, she is not much for countryside or beaches."
Go to Madrid and Lisbon 4 days each since you have not visited Spain or Portugal.
Fly into one take the train to the other and flight out the other.
But that Berlin mentioned below also has good Museums and no beaches or countryside.

I'd go to Berlin and Hamburg. Close together so you don't waste time traveling and there is so much to see in Berlin, you will be happy to have a week there. Hamburg is an exciting city too.

Time of year?

Sorry, should have mentioned that. Late June of this year.

With that timing you have some flexibility. I like the Ljubljana + Zagreb combo, or you could spend all of the time in Slovenia, perhaps just crossing the border to see Croatian Istria.

In truth, I'd probably start by checking to see what destinations are available via non-stop flights on the day I planned to depart from Ireland. That might eliminate a few of your options.

I would first check out which cities can be reached easily and cheaply from where you'll be in Ireland. Then choose among them.

Berlin has fabulous museums; and a trip there could easily include a day in Potsdam, also very interesting. I don't see Vienna on your list; but it is also a city of great museums and other urban delights. Paris and Lyon are easily paired and don't need me to expound on their attractions.
In my opinion, 8 - 9 days in Ljubljana and Zagreb would be far too many.

Hi,

I vote for Berlin and Vienna or Berlin and Krakow. Between the two you can take the night train or night bus...very doable and direct.

From your selection I am going like others with Berlin and would pair it with Warsaw. Both cities destroyed in WWII and rebuilt. They are not eye candies like Prague or Budapest but have certain vibe and excitement in them.

I would go to Skyscanner.com and type in DUB, SNN (or wherever you'll be in Ireland) as your From airport and Europe (or Everywhere) as your To airport. This will show you where there are direct, reasonably priced flights from your beginning destination. At that time of year, Northern Europeans are wanting to fly south so those fares tend to be more expensive. You might find some clear cut, or surprising possibilities by searching airline times and prices first.

Since you are going in the Summer, I would suggest a trip to Scotland. There is more to Scotland than Edinburgh. Rick Steves has some suggestions for touring Scotland.

Madrid and Lisbon are great places to visit, but especially Madrid in the Summer is hot.

It is a bit cooler in Portugal. If you decide not to go to Scotland, consider Portugal, Lisbon and Porto, with places near each city and between the two cities.

The other places you mentioned are great. Did a great river cruise from Lyon to Arles.

For cities with lots of urban excitement and museums, but (relatively) few tourists, I had a great experience in Glasgow, Manchester, and Liverpool. All are easy to reach from various Ireland airports. And they're not expensive at all - many of the attractions in these cities are free.

Here's my trip report with lots of details: https://community.ricksteves.com/travel-forum/trip-reports/uk-trip-report-glasgow-manchester-liverpool-in-september-2016

That said, if you're looking for art museums, Madrid jumps to the top of the list; the Prado alone justifies a trip there. (Although the weather in June probably isn't the most pleasant). And for sheer urban excitement and variety, you can't beat Berlin.

Slovenia and Croatia have a couple of nice mid-sized cities, but their countryside and nature are the best part in my opinion. You would have a hard time filling 8 to 9 days with only urban sights in Ljubljana and Zagreb and would be missing out on some jewels such as Bled, the caves, Plitvice, etc.

I loved Lisbon but instead of Madrid I would combine it wih a visit to Portugal's second city, Porto. It has a very different character to Lisbon and offers a wealth of sights. Between them you can easily keep busy for a week and there are fast train connections linking them.

Lisbon and Madrid are a great combo for sights, museums etc. however u will lose a day in travel betw these 2 destinations. How about choosing 1 and take short daytrips out? Both cities have very nice and easy day trips out.
I know these 2 cities and they are a wonderful visit and transport from Ireland by Ryan air could even be non stop.

How about combining Vienna and Salzburg or Munich? Munich has some good museums and Salzburg is a pretty little city. Or you might take a Baltic cruise and let the cruise line worry about your visa for Russia.

Thanks so much to all of you for the excellent suggestions, really made us think about several different options. Appreciate it!

Of the cities you are considering, I have visited Madrid, Berlin and Milan and would recommend any of them. Each has museums and other major sites. They also have opportunities for exciting day trips. Athens is also worth your consideration!

For those of you who have visited Madrid, is a one day/night trip to Valencia a good idea? From what I see online, it looks pretty cool! But it's not in Rick's Spain book.

Valencia is a bit far from Madrid. I would not try to do a day trip there.