The Natural Arch or Silathoranam in Tirumala hills is a notified National Geo-heritage Monument. It is a unique geological feature near the Chakra Teertham in Tirupati district of Andhra Pradesh. The arch is called Silathoranam in Telugu which means sila means 'rock' and thoranam means 'garland'.
It connects two vertical columns or an arch. The arch measures 26.2 ft in width and 9.8 ft in height and is naturally formed in the quartzites which is a very hard rock that forms when pure sandstone made of quartz is changed by heat & pressure. It doesn't have any layers. This silathoranam was formed due to natural erosive forces.
According to myths related to the arch, linked to the famous Tirumala hills temple of lord Venkateswara, the arch resembles the serpent's(snake) crown, a conch(Shankam) and a discus(chakram) considered to be the source of the idol of lord Venkateswara at the Tirumala hill temple.
The main deity in the Tirumala temple is of the same height as the height of the arch. Lord Vishnu, known as Balaji or Venkateswara at the Tirumala temple is supposed to have put his first foot down at a place called Srivari Padalu and the second step is at the location of the arch. Thereafter, the next step is stated to have been placed where his idol is now worshipped in the temple at Tirumala.
Tirumala bus stand is located at a distance of around 3.6 KM from the Silathoranam. You can reach the Silathoranam by taking a local taxi or the sightseeing bus from the bus stand.