What type of rock is Sigiriya rock made of?

The Sigiriya Rock was built on a granite rock created under the crust of the Earth, sufficiently strong to last for ages to come. The archaeologists have deduced its approximate height to be around 200 meters, from its very bottom to its very peak. The fortress is perplexingly strong and grand-even in its ruins. That is mainly due to the strength of the rock on which it was established.