As the heroes proceed to the upper level of the Mausoleum, it becomes apparent that it was once part of a larger building that fell into disuse. Judging from the jerry-rigged bridges and woodwork, this still-crumbling structure saw use after the original inhabitants left. Reaching the uppermost levels reveals this to be a cathedral-like building, like the Desecrated Temple. The heroes will travel first upward from the depths of the Mausoleum to the upper levels, then back down the other side to reach the exit.
There is a Runestone here, but it's easily missed. After crossing the bridge (that requires the middle half to be lowered), heroes can destroy the corner wall at the far end to reveal a switch. This switch raises another switch, upon which a helpful Leg of Ham resides, that raises a ramp to a small ledge that contains a pile of Treasure and a chest. Destroying the wall here reveals the rune. This isn't so much a dangerous area as a long one that demands endurance.
Much like the Haunted Cemetery before, this is a "gothic" remix of the mini-series' theme.