well I recommend you do go I go every year as I have family there. It is a lovely city and there is lots for tourists to do. There is the Prague castle, a the old town square, Charles Bridge, the Jewish quarter, the old town, the new town (even thats hundreds of years old) the national theatre, boat rides on the river and the zoo and more. The views from the top of Petrin Hill are lovely and they are lovelier from the top of Rozhledna. You also said you like walks, well Prague is best explored by foot. Nightlife in Prague is also excellent and there are some amazing restaurants. A lot of tourists also don't know about what's south of Prague along the vltava river. There are lovely, scenic views and walks and it is really beautiful. If you plan on staying longer in the czech republic (see website below)
visit.
http://www.panoramio.com/photo/10182466
http://www.panoramio.com/photo/14180186
There are very nice mountain ranges as well if you are interested in cycling or hiking and skiing is very popular in the czech republic, there are beautiful mountains in the czech republic if you like that sort of stuff.