St Michael's Chapel was built in the 14th century on a cemetery which was then moved underground into an ossuary. Perhaps that's the reason why it was named after Archangel Michael who is supposed to weigh the souls of the deceased whether they are worthy to go to heaven.
In the 18th century, the cemetery was replaced by a park that still exists to this day. It's interesting to note that bones were found as deep as eight stories underground.
It's possible to take a tour of the chapel as well as its underground area.
Sun - Mon: 1:00 pm - 6:00 pm
Tue - Sat: 9:00 am - 6:00 pm
Ticket: €1 - €1.50
Wikipedia https://en.wikipedia.org/wiki/St_Michael_Chapel
Address 2/3 Hlavné námestie, Košice 04001, Slovakia
Coordinates 48°43'11.689" N 21°15'30.272" E