Here's a clever trap door in the floor of a stair landing. I don't know it's particular use, but possibly for storage or storm shelter access.

This custom kids room setup includes several under floor storage compartments concealed by trap doors. These could be incorporated into many locations, and covered up with rugs.

The smugglers getting drugs from Mexico to the United States were caught stepping it up a notch in the last couple of weeks. In the small border town of Nogales, Arizona, authorities found pavement plugs in the metered parking spaces ...

Hidden priest hole room below trap door in floor

Trap door leading to secret room at Castle Menzies

Concealed stage trap door

Trap door leading to underground vault housing clandestine drug operation

Trap door in floor

Kitchen island concealing secret trap door to underground tornado shelter

Secret trap door to crawlspace