These ruined walls once were part of a chamber on the Platform of the Knives, so called because a dedicatory cache of stone knives was discovered in the course of its excavation. These walls are a good example of building technique in the Puuc region, where a shapeless mass of stone and lime mortar forms the core of a wall defined on its outside by a thin veneer of carefully dressed stones. Once set, the stone-and-mortar core of walls and vaults basically became one unit, its strength as a building material not dissimilar to modern concrete.