Europe or Bust!

After several years of wanting to travel internationally, I finally broke down and bought plane tix to go to Prague! I will be leaving in 7 weeks. I have so much to plan between now and then. I think I may have over booked my schedule. I will be in Central Europe for 3 weeks total. If any of you who have been to the Czech Republic or surrounding countries have ideas on what I absolutly need to see please let me know.