3 places
There is a modern art exhibit/gallery inside the building. Afterwards go for a dinner on the top floor to see the charming Prague.
To look for the entrance just go through the tiny sales office for concert tickets. The paintings in the church and the subtle beauty of some of the art pieces inside are worth your visit.
If you plan to visit the Kafka museum during your trip to Prague, you can buy a 50% off ticket at the Mucha museum.