The photo was posted earlier this week in the Facebook group Things Found In Walls - And Other Hidden Findings, where an unnamed hotel guest asked others what was going on.
They wrote: "I'm in a hotel and I just noticed that the bath drain has a light coming from it. What could it be?"
The photo shows a pretty standard-looking bath in a hotel bathroom, with tiled walls and a shower curtain.
If you look a little more closely, however, you'll notice there's a strange orange glow coming from the plughole.
Users commented to say the mysterious light was 'creepy as f***', with one saying it looked like something out of horror movie It. They wrote: "Uh dunno, but if someone down there asks if you'd like a balloon, just say no."
Another added: "That's clearly a portal to hell."
Some people, however, actually took a stab at answering the hotel guest's original question, offering up some explanations for the bizarre glowing light.
One person suggested: "Most hotels have a chase between the rooms where all the mechanical systems are exposed so they can be maintained.
"If the trap in the tub is plastic and the maintenance person left the light in the chase on, it will be visible in your room. That's probably what's happening here."
Sounds a lot better than Pennywise's new lurking spot, that's for sure.
Recently, another social media user shared a video of a similarly confusing set-up in their house, which comes with a random secret lair.
In the clip, TikToker @sancho483 can be seen giving a tour around his property, eventually coming to a bookshelf.
He then pulls on a lever, which sees the bookshelf opening up into a set of stairs that lead down to a secret area of the house.
After stepping through the opening, the man walks down the steps, which are dimly lit with candles, and into a huge room, which he says is under construction.
Those who watched the video were in awe of the creativity, though some admitted it looked like something much more sinister.
Commenting on the post, one user said: "HIDDEN MURDER DUNGEON, sorry I've been watching too much of Criminal Minds."
Another joked: "I watch too many movies to know that's most likely where a serial killer is hiding."
A third wrote: "I don't even have a broom cupboard and y'all got an entire secret lair."
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