Mardaneus's Cellar is a location in Aleroth in Divine Divinity.
From the cellar entrance, one has the choice of 4 doors, two to the south and two to the north. Both northern rooms contain barrels, crates and various broken items strewn across the floor as does the south-east door. The north-east room contains a lone skeleton.
The south-west room is similar to the others, with the exception of a locked door on the south-east wall. The key to the door is on the crate to the left of the door the hero entered. Passing through this door leads to a small annex with another door to the south.
Passing through the second door opens up into the room directly underneath Mardaneus' house, with a ladder to the north-west of the room, giving entry through the trapdoor.