The monuments of Champa, though considerable in size and number, are inferior to those of Camboja. The individual buildings are smaller and simpler and the groups into which they are combined lack unity. Brick was the chief material, stone being used only when brick would not serve, as for statues and lintels. The commonest type of edifice is a square pyramidal structure called by the Chams Kalan. A Kalan is as a rule erected on a hill or rising ground: its lowest storey has on the east a porch and vestibule, on the other three sides false doors. The same shape is repeated in four upper storeys of decreasing size which however serve merely for external decoration and correspond to nothing in the interior. This is a single windowless pyramidal cell lighted by the door and probably also by lamps placed in niches on the inner walls. In the centre stood a pedestal for a linga or an image, with a channel to carry off libations, leading to a spout in the wall. The outline of the tower is often varied by projecting figures or ornaments, but the sculpture is less lavish than in Camboja and Java. In the greater religious sites several structures are grouped together. A square wall surrounds an enclosure entered by a gateway and containing one or more Kalans, as well as smaller buildings, probably for the use of priests. Before the gateway there is frequently a hall supported by columns but open at the sides. All known specimens of Cham architecture are temples; palaces and other secular buildings were made of wood and have disappeared. Of the many sanctuaries which have been discovered, the most remarkable are those of Mi-son, and Dong Duong, both in the neighbourhood of Tourane, and Po Nagar close to Nhatrang.