Prague is by far the most popular destination of the country. Its choices of accommodation are tenfold compared to the second biggest spa town, Karlovy Vary.
Brno is the second biggest city of the country, which is also a well-known university and festival city.
Of the smaller cities, Cesky Krumlov in the south and its Old Town encircled by a river, is a popular destination. There’s another similar town nearby, Ceske Budejovice, but it attracts way less tourists.