This cupboard is a small room off the Dungeon Corridor, just before the dungeon hall. This room was where Rubeus Hagrid hid Aragog in the early 1940s.

The Potions Classroom is where Potions classes are taught.

The Slytherin Dungeon is located behind a wall in the dungeons of Hogwarts. A Password spoken to the wall is required to enter it; whereupon a passage is revealed leading to the Common room -- a low-ceilinged, dungeon-like room with greenish lamps and chairs.

The Hufflepuff Basement is the common room for Hufflepuff students at Hogwarts. The entrance to the Hufflepuff Basement is hidden behind a still-life painting near the kitchens.

The Hogwarts kitchen is located directly under the Great Hall, down the same staircase that leads to the Hufflepuff Common Room. It contains tables identical to those in the Great Hall and are directly below them; food must simply be placed on the tables in the kitchens, and it magically appears in the Great Hall.

There was a storage basement under the Potions classroom at Hogwarts Castle. It was accessible via a trapdoor and it was used to store cauldrons, ingredients and phials.