The Citadel is an archive of information for George R.R. Martin's A Song of Ice and Fire.
New to the series? Read our spoiler-free review of A Game of Thrones.
George said that artists have trouble with Dragonstone because they draw it like a normal castle with dragon statues adorning the walls. It is the only castle in Westeros built by the Valyrians and they had a powerful magic which could liquify stone and shape it how they want. (Inspiration for Stone-made-soft in the Long Price perhaps?) So Dragonstone is literally shaped as a dragon with doorways opening in their mouths.
The Westeros network consists of several different sites, including a forum and a wiki, for all your A Song of Ice and Fire needs.