Just a stone's throw away from the astronomical clock in Prague, the Illusion Art Museum is a perfect hideaway from the hot weather when you're in the middle of exploring Prague's historical centre. It is the first museum of its kind in Czech, exploring the art of illusions and tricks. The exhibition is highly interactive and taking a lot of photos is more than recommended!
The museum is located here, with a lovely view of the astronomical clock (Orloj). The tickets prices are 250 CZK for an adult and 150 CZK for a student (full price list here). For more information, see the official website (in English).