 The structure is described by Historic England as a gazebo and eye-catcher in the Castellated Gothick style, and is constructed in rough-faced stone with ashlar dressings.The Observatory was designed by (or follows a design outline of) Robert Adam, and dates from 1754–1770.It provides very fine views of Alnwick Castle, Hulne Park, Hulne Priory and other of the Duke's local possessions; a 360° panorama of the local area, farmland used for fox hunting and point-to-point horse racing; and distant views of Dunstanburgh and Warkworth Castles and the Farne Islands.