The Burns Family Mausoleum is, as its name implies, a free-standing building that contains the graves of the Burns family. Located within the boundaries of the Springfield Cemetery, it notably houses the remains of Ebenezer Burns, Vlad Burns, Cordelia Burns, Benedict Burns, Chastity Temperance Burns, Tom Marvolo Riddle Burns, and John Wilkes Burns. It also holds the remains of the Gaslight Killer, as showed in the second Great Phatsby episode.
The Burns Family Mausoleum first appeared in the opening scene of the non-canon Halloween episode Treehouse of Horror XII, in which it was depicted as being located on the grounds of Burns Manor. The mausoleum made its first canonical appearance in C.E. D'oh, where Mr. Burns tranquilizes Homer and attempts to wall him inside the mausoleum for stealing his plant. However, it takes him so long to lay the bricks in the wall that Homer easily escapes while Burns is too preoccupied with building the wall. The mausoleum later appeared in The Great Phatsby, albeit with a different design. (Note that in Treehouse of Horror XII, Burns Manor itself looks markedly different than in the rest of the series.)
The Treehouse of Horror design also appears in the mobile app The Simpsons: Tapped Out, in which it was released as a limited-time building on October 4, 2016, as part of the Treehouse of Horror XXVII Event.
In C.E. D'oh, Mr. Burns shows Homer his family mausoleum, where he shot him with a tranquilizer dart and tried to bury him within the mausoleum's walls with bricks. However, due to Burns' weakness, he is only able to place a few bricks and cement them into the entryway. Homer wakes up and walks out easily as Burns continues to build a brick wall (however, as shown in The Great Phatsby, the brick wall was removed).
It appeared once more in The Great Phatsby Part 2. After Burns is left bankrupt by Jay G, he isolates himself to his family mausoleum. When Homer encounters him there, he admits he went back to the plant. However, he decides to get back at Jay G with Burns, and holds a revenge meeting in there with him the next morning. After that, Bart joins them.