The Slytherin common room had one of the most extraordinary locations at Hogwarts because it was situated beneath the waters of the lake. While other houses enjoyed views of the castle towers or grounds, Slytherin students could admire an underwater landscape through the windows of their own common room. The common room was located in the dungeons, behind a stone wall that opened with a password. It was a long room with a low ceiling, dark furniture, greenish lamps, and large windows that allowed a mysterious green light filtered through the lake water to fill the room. Through those windows, students could observe the depths of the lake and the shadows of creatures swimming near the castle. The lake was home to merpeople, grindylows, numerous fish, and a giant squid. Although it was never confirmed that all these creatures swam past the windows, Slytherin students had a privileged view of that underwater world. What made the common room so fascinating was that it offered an experience completely different from that of the other houses. While Gryffindor had a cozy tower high above the ground, Slytherin enjoyed an underwater retreat surrounded by stone walls and green reflections. It was a mysterious, elegant, and magical place whose beauty was barely explored in the films.