Can anyone help me identify the title to a '70s Horror Movie my kid brother and I walked out of (scared to death I might add) back in the early 1970s. This was an army base theater, so the movie could even have been a few years old at the time we saw it, I'm not sure, but think it must have been made before 1974. Anyway, what I remember is a team of scientists, or possibly government types, discovering a smooth black cylinder deep underground. The characters spend a lot of time poking, listening, and digging around the smooth shiny black container, which ultimately proves to hold a kind of pure essence of evil, or the devil maybe, that they unwittingly release. Thanks a bunch.

Cheers.

Sounds like it could be Quatermass and the Pit? Great film...

Quatermass and the Pit (1967)

Thank you Kohoutek! You were corrrect, I purchased this film on eBay and it was the movie I was looking for.

Cheers