What looks like one enormous church is actually two separate buildings. A hidden three-foot-wide house separates the two structures. The house is so thin, it’s easy to mistake it for a wall. 

Igreja dos Carmelitas Descalços was built in the 17th century for Carmelite nuns, and Igreja do Carmo was built in the 18th century for Carmelite monks. Both churches are extravagant sights to behold, making it easy to completely miss the small, humble house standing between them.

There are a number of local stories about why these churches are side by side. The most common tale says it’s because the archbishops couldn’t get along, so one built a church next door to the other in the ultimate architectural spite move. But in reality, the churches don’t actually touch each other, thanks to the house wedged between them.

Local guides give two different reasons for the skinny house’s existence. Some chalk it up to an old law stipulating that two churches couldn’t share a wall. Others say the strange home was erected to keep the nuns and monks from getting too cozy with one another.

What’s most amazing is that people actually lived within the unbelievably narrow abode. It was even inhabited up until the 1980s. Now, visitors can buy a ticket to peek inside this most unusual sliver of a building.