The Dungeons at Hogwarts are located underneath the school and lacks a lot less light than any other areas of the castle. It's usually much colder down here than it is in the main corridors and classrooms due to the stone, lack of light and close proximity to the coolness of the Black Lake. The Potions Classroom is located to the left and the Slytherin Common Room and Dormitories are located to the right. It's fairly quiet in the dungeons, so you'll notice your voice echo off the stone. There are torches that line the wall in attempt to help guide students. Some say the Slytherin's could navigate the dungeons without light, just because they are so accustomed to the darkness of the dungeons.