I worked on a huge ruined country house site for English Heritage. We wanted to send cameras down the drains and culverts under the cobbled and paved stableyards.

Guy from the inspection company turns up, looks breifly at the maps showing where we think the culverts are, and then proceeds to use dowsing to find them for himself.

Not only that, he told us..."You got that wrong, its further this way" etc,etc. Amazingly, he then showed us where there were new drains and culverts that were not even on the drawings. Turned out he was 100% right.