I rented it on DVD from Blockbuster, possibly around 15 years ago. I think it's a group of American soldiers lost in Korea (might even be a Korean movie), who get trapped in a temple that is not in the real world. It might not be a temple. but is a large old building which is not normally seen.
Not a mainstream film, more like one of those Tartan Asia films as I recall. Could be way out on that though. These are modern-ish soldiers with assault rifles and such.
I think they are warned by locals not to go there. It's supernatural, not a man made trap or anything