Hello!
thats a very good idea to visit Czech! :) I recommend BRNO..thats where i live..there´s a Castle here surrounded by a nice park, Cathedral, many churches, Dam lake, Zoo...then you should deffinitely go see Olomouc, Telc, Trebic, Cesky Krumlov, Lednice..I havent mentioned Prague because thats where everyone goes haha..if you have more questions I ´ll be happy to answer them!
have a great day
Dashi