Designed by Robert Adam, the observatory was built between 1754 and 1770 by Hugh Percy, 1st Duke of Northumberland. The building is somewhat of a folly, resembling a castle ruin, but was built as a place for the Duke to stop during carriage tours of his estates. The elevated observatory room has windows on all four sides, and provides spectacular views of the surrounding countryside.

Information about Observatory at Ratcheugh Crag on Keys to the Past