The Third Floor Corridor

In Harry's first year, this corridor is forbidden to students. Fluffy was kept stationed within the corridor, guarding a trapdoor in the floor. The trapdoor allowed a person to drop down to below the school, into the chambers used to hide the philosopher's stone. Fluffy now roams the Forbidden Forest meaning that the corridor is no longer out-of-bounds, or that it is still kept locked up btu students still dont enter.