Located on a small island within a three hectare irrigation lake, Riverstone Castle is approximately 1250 sqm over three floors, incorporating a dungeon and underground tunnels. Four guest suites on the first floor open onto large roof decks on the east and west sides. Constructed of solid masonry and clad in large bolstered Oamaru stone blocks, the finished walls are almost half a metre thick. Decorative external features include turrets, castellated ramparts, gargoyles and carved Oamaru stone decorations embodied in the cladding. The entire structure is heated from a geothermal system which is laid across the bottom of the lake.