A dozen or so dead bodies are stored for all eternity in the basement of North Philly’s Church of the Advocate.

In the back of the cathedral, a spiral staircase leads down into darkness. It’s made of iron, annd reverberates with a clang each time your shoe lands on a step. At first, you’re guided by the light from the first floor — but that ends as you near the cement floor of the crypt.

Affectionately dubbed “bone houses” by Atlas Obscura, crypts have fashioned by humans for millennia. The famous one at Old St. Peter’s Basilica in Rome was built some time around the year 600 CE. It’s likely predated by other crypts in North Africa, Algeria and Istanbul.

The underground tombs fell out of style after the 10th century — and by the time the Gothic period came around, they were few and far between. Among American churches, crypts are a relative rarity. There are a handful in New York and Boston. In Philly, there’s a big one at the Cathedral Basilica of Saints Peter and Paul.

“Very few old churches in Philadelphia have crypts like we do,” said the Advocate’s Rev. Renee McKenzie, who’s watched over the church the last eight years. “Sometimes you’ll just see a wall with ashes, or burial places outside.”

It’s a creepy place. Besides the fact that the crypt has absolutely no source of light, it’s also swarming with cobwebs. True to cliché, there’s basically no way to view the actual tombs beneath the low ceilings without getting tangled in gossamers.

Assuming you’ve got a flashlight, the first thing you’ll see when you get downstairs is a giant rectangle with a crank and floor-to-ceiling ropes on each corner.

McKenzie explained the pulley system — how church leaders of yesteryear used to lower bodies down via a hole in the floor. A dumbwaiter for the deceased. A lift for the lifeless. An elevator for those who’ve expired. Whatever you call it, surely a lot easier than carrying a body down a spiral staircase.

Exactly how many people have lain in the Advocate’s basement? We’ll likely never know for sure, since the church’s past leaders rarely kept records.

What we do know: The Advocate was built in memory of George W. South, a merchant and Philadelphia socialite of the 19th century. So that dude and his family got first priority. George, his wife, his son and his accountant (yup) are all entombed at 18th and Diamond.

The Advocate’s first clergyperson is said to be there, and McKenzie knows that there’s at least one black woman buried in the basement, because during the Civil Rights movement, records show, the church made it a point to integrate the crypt.

To the reverend, much of the crypt’s past is a mystery. But she’s got a hunch it still impacts the present day.

“I’ve got the wealthy elites, their spirits hanging around the Advocate,” McKeznie said. “Then I have the spirits of all the ancestors who came here to protest for Civil Rights, they’re hanging out at the Advocate. The spirits that live on the murals on the walls, they’re hanging out at the Advocate. Who would be surprised there’s a clash going on in that place?”

“I’ve been mediating clashes ever since I’ve been here,” she added. “Clashes of the spirit.”