The Hungarian National Gallery, which takes up most of the space of the Buda Castle in Budapest is a very nice place to visit to see some of the best Hungarian fine art pieces, especially the 19th century Hungarian paintings.
If you wonder what the Buda Castle might be from the inside, or what the views are from its windows, it is also worth visiting the National Gallery, even if you are not a museum fan or gallery goer. The entrance fee to the National Gallery in the Castle is very cheap, it has a nice cafe, and the exhibitions will not bore your for an hour.
Hungarian National Gallery (Nemzeti Galéria) opening hours during December (except for Xmas and NYE, see below):
the general opening times of the National Gallery are as follows (almost all days in December)
Tuesday – Sunday: 10 am – 6 pm