Stush: Wow, that is a humongous and beautiful cactus! I don't know anything about cactus but Cereus peruvianus is a synonym for Cereus hildmannianus and that beauty in your photo looks a lot like Cereus hildmmanianus, possibly variety monstrose.
C. hildmannianus:
http://dendro.cnre.vt.edu/dend...
C. hildmannianus var. monstrose:
http://www.phoenixdesertnurser...
Cereus peruvianus is also apparently a synonym for Cereus repandus (the cactus in my photo.) There may be a lot of them with the common names of "Apple Cactus" because of the fruit that resembles little apples.
