Allow about 3-4 hours to do the full tour of the buildings and gardens, more if you want to visit the museums as well (extra cost). Very well organised place so easy to navigate to the different buildings. My favourite was St Vitus Cathedral - very impressive as far as cathedrals go. It costs extra to climb the tower. You also pay extra to get a photography licence - one (50 koruna) was fine for my friend and I but no one asked to see it. Easy to get to by tram including no. 15, 22 and 23
We went in late summer and it was still quite crowded. Not too bad though. Wouldn’t go there in high season. The cathedral is beatiful but still what you would expect if you’ve been to other great citis in Europe. The rest of the castle is rather ordinary or downright disappointing.