Trip without kids

A while back I mentioned that we had decided to go on a trip without our kids. I am so excited. We haven't had a vacation without them since 2005. It is always so hard to figure out who is going to watch them, how are we going to get them there and all that other stuff. Lucky for us my mom and sister are willing to watch them for what is going to be about two and a half weeks. We have decide to go to Italy and Spain. We are going to hit the towns of Rome, Venice, Barcelona and Madrid. We have never been to Europe.

Let me know if you have any tips on traveling over there or on any of these cities!