It might sound grotesque, but bones have been an architectural staple for millennia. Here are some of the world’s greatest osteological marvels.

1. The Skull Tower of Niš

Using the skulls of your enemies to build a tower sends one powerful message—even if the structure winds up measuring a scant 15 feet in height. In 1809, midway through the first Serbian uprising against the Ottoman Empire, Turkish general Hurshid Pasha gathered 952 rebel skulls for this grisly project near the city of Niš. All but 58 were later removed and given dignified funerals, but thanks to the Serbian government’s preservation efforts, you can still see the building today.

2. The Czermna Skull Chapel

Smithsonian

This unique temple is adorned with some 3000 skulls and countless shin bones. Vaclav Tomaszek, a priest residing in the small Polish villiage, collected and assembled the necessary skeletal remains from 1776 to 1804. Where did he find so many bodies? A combination of recent disease victims and mass graves hastily left behind by the Thirty Years’ War gave him more than enough.

3. The Seldec Ossuary

Also known as “the Kutna Hora bone church,” this Czech building looks like an unassuming monastery on the outside. But venture indoors and you’ll see a bony chandelier, a bony candelabrum, and strings of assorted bones dangling from the ceiling.

4. The Capela Dos Ossos

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Evora, Portugal is home to yet another worship center built with human remains. Local history maintains that, during the 16th century, a few nearby cemeteries were destroyed, unearthing some 5000 corpses. The cathedral’s resident monks began putting them on display and utilizing them in the structure’s very framework, where they came to serve as a glaring reminder of death’s inevitability. Above the chapel’s doors is this haunting message: “We bones that are here, for your bones we wait.”

5. The Eggenburg Charnel

Atlas Obscura

The remains of 5800 Austrians were utilized in this marvel of ghoulish beauty, which was largely constructed in 1405.

6. Dinosaur Bone Cabin

Courtesy of Yelp user Jessica H

It isn't just the bones of Homo sapiens that have been converted into building materials. Wyomingite and gas station owner Thomas Boylan finished assembling this piece of prehistoric real estate in 1933 (luckily, dinosaur fossils are quite abundant in the cowboy state).

7. Our Lady of the Conception of the Capuchins

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Beneath this Roman church lie the meticulously-arranged bones of some 4000 friars laid out to form a myriad of gorgeous designs (including stars and flowers). A few have even been posed like ghostly mannequins under drooping robes.

8. Cattle Bone House

Dan Phillips of Texas has been building houses with recycled materials for over 15 years, and cites cattle bones as one of his favorite materials. One particular home he oversaw in the eastern part of the state used bovine skeletons to forge countertops, door handles, floor tiles, and patio furniture.

9. Mammoth Bone Huts

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Some of the oldest man-made dwellings in recorded history were primitive huts made with these ice age giants’ remains. The best-known examples hail from an archaeological site near the Ukrainian village of Mezhyrich.

10. Church of San Francisco

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The cellar of this Peruvian church features femurs, skulls, and other bones gingerly laid out in ornate circular patterns, which attract tourists to this day.

BONUS: Paris Catacombs

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Twelve million people currently inhabit France’s largest city. The bones of an additional 6 million have been laid to rest in the labyrinthine caves and tunnels which lie under it. Originally intended to tackle the area’s overflowing cemeteries, many of the skulls and other bones were later re-arranged to produce some truly eye-catching walls in this fascinating subterranean world.