Inside the fort is a kitchen area attended by a non-hostile old woman named Agnis, who also happens to be a target of the Dark Brotherhood. Everyone else in the fort is hostile, except when you complete the Battle for Whiterun for either the Imperials or the Stormcloaks. The area contains a cooking pot and a copy of Rislav the Righteous.
Fort Greymoor Prison
This is a smaller area containing a number of cells.