Old Town Square Prague

This has to be explored on your first day. Make it your slow day. Take a walk around and absorb the beautiful buildings and the energy of the people. You can sit at one of the cafes when you are tired and just people watch. Or you can get ice cream there. My advice is to get ice cream before you come here from a place close to the hanging man. It says it's the best Italian gelato in Prague. It really is so trust me on that!
The square has tourist attractions office where you can book hop on hop off tickets, boat ride ( did mine on sunset time) and many more. You can also ask for a tour on horse carriage right at the square. During summer days, this place can get hot so come back in the evening and experience the night life. Everyone sits on the floor and enjoys a drink and connects to people. If you don't drink then just get a kebab on the way and a soft drink then relax on a bench or the floor and watch everyone let their hair down. Of course meet new people or just sit in silence and be in the moment.