The flat roof system is predominantly used at the Someshwara Temple, wherein flat slabs of stone are laid horizontally, spanning from one supporting beam or wall to another (see the section on the Post-and-Lintel system.) The central aisle of the mandapa is also spanned by a flat roof, though raised to a higher level than the rest of the hall. A layer of lime surkhi (lime concrete) is then laid over the flat stones, sloping towards the edge of the structure to effectively drain off rainwater. Finally, this is topped by clay tiles. This flat roof allows for emphasis to be placed on the pyramidal tower (vimana) of brick and mortar that rises above the sanctum. The gopura, which is also in the form of a stepped tower, is crowned by a barrel vaulted roof, also known as shala roof. Here, the intermediary floors are constructed using the traditional system of Madras terraces.