In my company's old office, we had a concrete floor on the lower level. Once, we had a halloween party and taped a pentagram to mark the dance floor (this is just like a Buffy episode isn't it?)

The next day after the party, we pulled up the tape but so much beer had been spilled that even after cleanup, the concrete held a darker colour where there wasn't tape, so the pentagram was still clearly visible.

For months.

And it was right under the spot where devops + security teams sat.