Which of the following structures is often used for multiple interments in vertical spaces?

The structure that is often used for multiple interments in vertical spaces is the mausoleum. A mausoleum is an above-ground burial structure that can contain multiple spaces for entombing the deceased, typically allowing for vertical stacking of burial chambers or crypts. This feature makes mausoleums an efficient solution in areas where land may be limited, allowing families to memorialize multiple generations in a single location while conserving ground space.

Mausoleums vary in design and size, ranging from small family structures to large, elaborate buildings that serve a community or a specific group. They provide a dignified and preserved environment for the deceased, with the added benefit of maintaining the remains in a controlled atmosphere.

While a columbarium is also designed for interments, it specifically accommodates cremated remains stored in niches, as opposed to traditional burials. Graves refer to earth-covered burial sites and are not designed for vertical multiple interments. Memorials typically refer to markers or monuments commemorating the deceased but do not involve actual interments. Thus, the mausoleum is the correct answer due to its ability to facilitate multiple entombments in a vertical arrangement.