Possibly a tornado shelter? Security Pod (aka Urban Foxhole) that can be installed under your existing garage floor or a concrete slab. The Security Pod can be used as a panic room, a secure storage vault or a survival bunker.
I like this idea for the ladder. Organize your garage in one morning. Ladders low on walls. Attach BC plywood on wall (one side smooth), hang wire baskets with mirror support hooks, hang bikes from a large hook set at a downward angle.