Be very careful when exchanging money in Prague city center (area around Vaclavske namesti). Companies like MoneyUnion, Cash Exchange usualy show the exchange rates on a screen but when you want to exchange money they will give you contract with completely different exchange rate! Look twice before signing. My yesterday experience in subway below Legerova street towards Muzeum was CZK/EUR exchange rate 27.21 CZK for EUR but on a contract they offered 16.71 CZK for EUR. I didnt py attention and was ripped off... Hope it helps to others.