Built after 1325 by King Charles I of Hungary (although accounts seem to differ both on time and builder) this palace once had 350 rooms but now is only a shadow of its former grandeur. It served as the home of Hungary's rulers until the Turkish Ottoman invasion, when it was destroyed and later buried in a landslide. Archeologists found parts of the ruins in the 1930s and reconstruction has been going on since then.
The tourbooks I have on Hungary seemed to give it only a minor mention, but quite frankly I felt it was fascinating, with excellent displays of reclaimed artifacts and nicely done reconstructions. The site is quite large, and with time I'm sure it will become even more interesting.