Arguably the warmest new attraction in town is the Papilonia Butterfly House which opened last summer. Located on the lowest level of Hamleys' toy shop on Na Příkopě (around the corner from Wenceslas Square), the permanent attraction covers 150m² and its design was inspired by the temple of Angkor Vat in Kampuchea.
The environmental controls maintain a temperature of 26ºC and 80% humidity and the attraction is home to 600 butterflies from 40 different countries, including Mexico, Australia, and other South American and South East Asian locations. The intention is to vary the species during the year so there will be different species in the spring compared to the autumn.
Because of the humidity cameras may get a bit steamed up, especially coming in from the cold. My new iPhone X had no problems, but my Nikon DSLR couldn't cope so it went back in the bag. You can get up really close to the 'models' which continue to pose even when you're just a few centimetres away.
This was a wonderful experience and at the time of writing cost 150CZK for adults. The collection is open every day from 10:00am to 20:00pm (8 o'clock).