Situated on a strong site Hollows, or Gilnockie's Tower, is a rectangular 16th century tower house of four storeys and a garret within a corbelled-out parapet. There was probably a courtyard.
The entrance leads to a turnpike stair which climbs to the upper floors. The basement is vaulted, and the hall on the first floor, has a wide moulded fireplace.
Hollows was a stronghold of the unruly Armstrong clan after nearby Gilnockhall or Gilnockie Castle had been destroyed by the English in 1523. Johnnie Armstrong of Gilnockie was hanged without trial by James V in 1530, with 50 of his family, as recorded in the old ballad. A stone memorial marks the mass grave at Carlanrig.
The tower has been reroofed and restored, and now houses the clan Armstrong Centre, although the Armstrongs were never a clan.
There may have been another tower to the south, known as "Priore Johns".