Situated the cemetery a short distance to the northeast of the former Westerkirk Parish Church, Bentpath, the Johnstone Mausoleum is a remarkable classical edifice, which was designed by Robert Adam (1728-92) for John Johnstone of Alva, for his father Sir James Johnstone of Westerhall (1726-94). Built in neat droved ashlar, with a prominent dome, the front features two pairs of columns supporting a pediment and frieze decorated with ox-skulls. The building was restored by Solway Heritage in 1998.
It is similar to John Johnstone's own mausoleum in Alva Cemetery (Clackmannanshire).