We went on the free walking tour with Sandemans (red umbrella in square). Our tour guide Lyle was originally American but has lived in and LOVED Prague for many years. I can't recommend this tour enough and try and book Lyle, do it on your first day as Lyle not only gives you a history of Prague but some great tips for your stay in Prague, including exchanging money, local phrases, places to eat, shop, visit. I could go on!!. His historical knowledge is simply vast, how he remembers it all makes my head spin! And he tells the local history with such a great enthusiasm, we were totally drawn in by it and the tour flew in. I won't spoil the tour for you but I will say he gave us some fantastic tips of where to visit that I didn't even know about. This tour really shaped our visit to Prague and would really recommend, the tour is free but the tour guides live off tips so considering how helpful and knowledgeable these guides are dig deep folks, it's a bargain!