The “Gate to Hell” in Hieropolis, Turkey will now be open to the public. It was only rediscovered in 1965 and its “mysteries” explained in 2013:
The explanation for this mysterious religious site is fascinating. At the site, healthy animals were led down by priests to the entrance and they died quickly, but the priests who had accompanied them (miraculously) returned unharmed. These “miracles” had geological explanations:
Here is a wonderful video on the site:
https://greekreporter.com/2022/06/23/ancient-gate-hell-hierapolis/
Hieropolis, Turkey