The YouTube channel [Abandoned Seekers](https://www.youtube.com/channel/UCMbWhn8YHjHcfToxD7M1k8A) is exploring quite an amazing location. Maenofferen slate quarry is an old mine that dates back to 1800! Incredibly, the mine was in operation in some form until the start of the 21st century! The mine is abandoned nowadays, but there's still so much history inside. With over 200 years of operational use, there is certainly a lot to explore.