The Potions Classroom is where Potions classes are taught. The classroom used to be squared-sized, very large, with large tables and windows. From 1992-onwards, the classroom was of an oval shape and relatively smaller, with small work tables. In 1996, the classroom was extended, adding space for more work tables.

The office used by Severus Snape during his long tenure as Potions master at Hogwarts School of Witchcraft and Wizardry was a gloomy and dimly-lit room found in the school Dungeons. The shadowy walls were lined with shelves of large glass jars filled with slimy, revolting things, such as bits of animals and plants, floating in potions of varying colours. Snape's collection grew over time – in 1994, Harry Potter noted there were more jars than in 1992, and by 1996, there were hundreds of them. The office had a fireplace. In a corner, there was a cupboard containing Snape's private stock of Potions ingredients. In 1997, the office also contained a table, but it is unknown if it had been there before. The office is sealed with a spell only wizards can break.

The Slytherin Dungeon is located behind a wall in the cellars of Hogwarts School of Witchcraft and Wizardry. 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. This dungeon extends partway under the lake (which is why it has green-coloured lamps). The common room has lots of low backed black and dark green leather sofas with buttons, skulls, and dark wood cupboards. It has quite a grand atmosphere, but also quite a spooky, cold one.

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

The cellar is decorated with yellow hangings and filled with fat armchairs. Underground tunnels lead off to the students' dormitories and all the doors are perfectly circular.