Winterfell

Winterfell is a castle in the North of Westeros. It is the ancestral home and seat of power of House Stark, which has ruled the North for millenia. It was supposedly built by Brandon the Builder with the help of giants. It lies on the Kingsroad that runs from King's Landing to the Wall. Built on top of a hot spring, it uses the water from that spring for heating, making it more comfortable than other castles during the harsh northern winter. Under the castle there is a crypt where the Starks bury their dead. There is a 'winter town' outside which is apparently mostly deserted during summers, but where the smallfolk gather in winters. Wintefell is encircled by two massive granite walls with a wide moat between them. The outer wall stood eighty feet high, the inner more than a hundred.

The castle was sacked and burned down by Ramsay Snow. The crypts remain intact. Source: AWOIAF