Prague’s outdoor swimming pools are opening their gates for the 2025 season. From Petynka in Prague 6 to Hostivař reservoir in Prague 10, here is everything you need to know before heading out — opening hours, ticket prices and what has changed this year. Hostivař Reservoir and Radotín Biotope already welcoming swimmers The Hostivařska přehrada in Prague 10 is one of the most popular summer destinations in the city.