Trees
The Aokigahara Sea of Trees at the base of Mount Fuji, west of Tokyo, is the second most common place for suicide in the world after San Francisco's Golden Gate Bridge. It could be because of the spiritual significance of Fuji, the dense silence of the forest or the fact that compasses won't work there, as a result of huge magnetic iron ore deposits. Some 50 corpses a year are recovered in various states of decomposition by forestry workers. Unsurprisingly, the forest is now full of signs such as "Please reconsider!" and "Consult the police before you decide to die!"
I must have found all the areas in UK forests with similar iron ore deposits
Maybe when using those forests we should have signs up saying "Please reconisder whether you should orienteer here!" and "Consult the police before you decide to orienteer!"