Another great opportunity to visit hidden and closed buildings.  During these days many buildings around the City of Prague will be open to the public.  You will be able to see building and areas normally closed to the public.  Lectures, exhibitions and concerts are also on the program.  If you want to go outside of Prague to enjoy some other areas, go to the website to see what other interesting buildings and cultural monuments will be open around the Czech Republic.  Mostly free but there is a fee for some events so check on their website.