The external walls were usually built of coralline limestone, which is harder than the globigerina limestone used in the internal sections of the temples. The softer globigerina was used for decorative elements within the temples, usually carvings. These features are usually sculpted in relief, and they show a variety of designs linked to vegetative or animal symbolism. These usually depict running spiral motifs, trees and plants as well as a selection of animals. Although in their present form the temples are unroofed, a series of unproven theories regarding possible ceiling and roof structures have been debated for several years.