Berlin and Prague are no-brainers. Cheap (if you avoid the tourist ripoffs in Prague) and fun. I did the free walking tours from Sandemans (http://www.neweuropetours.eu) in both and they're awesome. I did some of their paid tours too and they were worth it imho.

Paris and Amsterdam can be done reasonably if you're careful too. This card http://www.amsterdam.info/museums/museumkaart/ is good value if you like museums -- there are a ton of them in Amsterdam. Don't bother with the tourist card though, it's too expensive and you can walk almost everywhere.

Never been to Luxembourg or Vienna. Either I'm underestimating them or they aren't interesting by comparison.

I totally agree with doing Venice but beware -- it's *crazy* expensive. I also agree with Lisbon. It's pretty cheap and has a pretty fun relaxed vibe -- street parties every night, beaches nearby, and medieval castles and monastaries. Barcelona is on my list but I suspect Lisbon is kind of a smaller more relaxed variant of it.

You can get outside of western Europe too to places like Tallinn and Helsinki. Norway is pretty cool if you like hiking at all. Stavanger has some great day hikes accessible by public bus from the city (look up Preikestolen and Kjeragbolten). But Norway will break the bank if you eat out or go to bars.


As far as booking flights. If you're booking an award don't just book a simple round trip. United transatlantic awards allow a stopover and it doesn't matter what routing you take (within the allowable routes). So flying to Prague via Frankfurt costs exactly the same number of miles as flying to Paris, spending a week there and then flying (you can even spend up to 24 hours in Frankfurt I believe) to Prague and spending a week there before returning.

And plus you can *also* book an open jaw. So instead of returning from Prague you make your way by train to Berlin and then Germanwings or Air Berlin to Amsterdam, then have your return flight from Amsterdam back home. (In fact you don't have to return to the same airport either. You might decide to add on a flight to someplace else in the US and book a separate one-way to get back home from there).

c.f. http://hackmytrip.com/2012/07/maximi...aws-on-united/