My girlfriend and I are going on a little trip around half of Europe ... for 26 days. ^_^

For those who care:
We're using an InterRail Pass and travelling by train. We're leaving in 2 days time (wed 22nd at 6am) and we should get back on the 16th August. =] We're planning on going to Paris, Lisbon, Barcelona, Nice, Florence, Vienna, Cologne, Lile and then home. Any ideas on cool things to do/see in any of those places would be amazing. ;)