1) Prague Castle
Let’s start with some free things to do in Prague: the greatest dominant feature of the city is the Prague Castle, which appears on every single postcard from Prague. Thanks to its marvelous position high above the river Vltava it could be seen from many other spots and it offers a spectacular view on the city center. In the area surrounded by ramparts there is one of the most magnificent religious buildings in the Czech Republic, the St. Vitus Cathedral. It has a thousand year old history and that is precisely why you can find three elements from every architectonic style to neo-gothic style to modern architecture.
Take a walk around the area and you´ll find beautiful gardens, churches, Belvedere, the most magnificent work of Italian renaissance in the North from Alps and the Golden Street that was for some time home to the poet Jaroslav Seifert. However, the funniest thing to do which can´t be forgotten is to try and make the castle guard laugh :)
2) Old Town