Have you been there already? 
St. Matthew’s Fair (Matějská pout´) is held at the Exhibition Grounds in Prague, where you will discover traditional and new attractions: a rollercoaster, a centrifuge, a haunted castle, swings, rocking boats etc.
Open daily 
Entrance fee: free (weekdays) or 30 czk (weekend).
Cost: from 40 czk 
This Fair is open till 21 of April!
Address: Výstaviště 67, 170 90 Praha 7 
Tram 6, 12, 17, stop “Výstaviště Holešovice” 
https://www.instagram.com/p/BRS-ENmDNen/