Silathoranam is a natural rock formation in the form of an arch, near the Chakra Tirtham. Geologists have identified the rocks on the hill as pre-Cambrian, and this arch formation suggests an antiquity of several million years to the Tirumala hill.It is said that there are only two other natural rock arches of such great antiquity in the world.
Source : http://www.tirumala.org
