The Lost Tunnel is a dungeon at Hogwarts School of Witchcraft and Wizardry. It was built by Salazar Slytherin in medieval times, keeping it in secret. It is located in the Hogwarts Dungeons, "miles under the school", in the antechamber, called the Corridor of Secrets, to the Chamber of Secrets. It is full of slugs and it seems that nobody has entered the tunnel for ages.