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.
Mr. Martin does not approve of people starting A Song of Ice and Fire MUDs or MUSHes without first obtaining permission from him to do so. Currently only one such game is approved: Blood of Dragons MUSH. Excerpts from relevant e-mails regarding the approval can be found at the Blood of Dragons MUSH FAQ.
The Westeros network consists of several different sites, including a forum and a wiki, for all your A Song of Ice and Fire needs.