Once a strong fortress and still an attractive edifice which can be seen for miles around, Udny Castle consists of a large altered 15th-century tower, which may incorporate older work, to which a huge baronial 19th-century mansion had been added – although this was demolished in the 1960s. The tower was heightened, and corbelled-out bartizans with pointy finials were added in the 17th century, along with a parapet on one side. The walls are as much as 8 foot thick, harled, rounded at corners, and pierced by gunloops and shot-holes.