1 Minnesota Jones: Well, we have a spare day or two while we wait for Miss Thoroughgood's return telegram, and for Sallah to arrive.
2 Monty: I suppose we could dig around out in the ruins of Tintagel Castle a bit.
3 Prof. Jones: I knew you'd turn around to my point of view, Junior!
4 Monty: I'm hoping to find a barrow with some wights who can teach you a lesson.

A barrow, also known as a tumulus is a mound of earth and sometimes stone built over the top of a grave site. They're astonishingly common in all parts of the world and come in many varying shapes and forms. It seems that to pretty much everyone, sticking your dead into the ground and then piling as much stuff on top as you can seemed like a really, really good idea.

Clearly they knew something...