Suzaku Castle

Suzaku Castle (朱雀城) is a large and (presumably) medieval-aged castle located in Japan. In all of its appearances in the Street Fighter series, as well as crossover games, it has served as Ryu's home stage.

Description
Not much is known about the castle itself, but it can be assumed that Ryu is associated with it some way, given that it has been his home stage every time it has appeared in a game.

In Street Fighter II, Ryu's stage, set on Suzaku Castle, has signs on it reading Fūrinkazan (風林火山), a shortened version of a quote from Sun Tzu's Art of War. The same message is seen written on Ryu's belt in some of his appearances.

Theme
Since any stage set on Suzaku Castle is associated with Ryu, any theme that plays on it is associated with him, as well (primarily the one from Street Fighter II).