The Fast Mansion is a house of race boat legend Tony Fast and his son Tony Fast Jr., that only appears in the episode "The Hot Shot." Tony Fast Jr. mentions his mom also lives there but she is never seen.
The outside of the Fast Mansion has pretty much what a regular mansion has. It was a grassy setting with a large wooden door that acts like a gate. It even has a speaker where one pushes the button in order to speak with the other as SpongeBob did to communicate with Tony Fast Jr.
The inside of the Fast Mansion is extremely luxurious. It has many rooms and fancy items. The biggest attraction may be Tony Fast's garage where he keeps all of his speedboats. Tony Fast Jr. tells SpongeBob how his dad won his races using these boats. Jr. even let's SpongeBob pick out his favorite boat to drive around in, which, SpongeBob chooses a red speed boat with flames and the number 8 on it. It is called the Baytona Classic.