The most sacred of Sikh shrines, the Golden Temple, is a major pilgrimage destination for devotees from around the world, as well as, an ever increasing popular tourist attraction. Construction of the Amrit Sarovar (pool of nectar) was initiated by Guru Amar Das, the third Guru, in 1570 and was completed by Guru Ram Das, the fourth Guru. His successor, Guru Arjan Dev began work on the building after inviting Mian Mir, the Sufi saint, to lay its foundation stone in 1588. Completed three years later, the Harimandar Sahib, or Darbar Sahib, as it is also known, required substantial restoration following its sacking by the 18th century Afghan invader, Ahmad Shah Abdali. It was Maharaja Ranjit Singh who oversaw the gilding of the shrine in the early 19th century, earning it its English moniker. In step with Sikhism's basic tenet of universal brotherhood and all-inclusive ethos, the Golden Temple is accessed from all directions. The main entrance is through an imposing clock tower, which also houses the Central Sikh Museum, and provides a stunning view of the shrine and its reflection in the Amrit Sarovar. Another entry is through the magnificent silver doors of the beautifully embellished Darshani Deori. It leads onto the causeway that connects the sanctum sanctorum with the Parikrama, the marbled surface surrounding the Sarovar. The lower facade of the Golden Temple is clad in marble, inlaid with precious and semi-precious coloured stones, using the pietra dura technique to create motifs. Within, the Guru Granth Sahib is enshrined on the ground floor, in a room embellished with splendid frescoes. The Parikrama is marked by a number of shrines and memorials of spiritual and historical importance. These include the Dukh Bhanjani Beri, the gilded chhatri of Ath-sath Tirath, a memorial to Baba Deep SinghandGurdwara Lachi Ber. Close to the Darshani Deori lies the Beri Baba Buddha, another revered site. Baba Buddha lived for a 120 years and had the opportunity to serve five Gurus during his lifetime. He oversaw the construction work at the Amrit Sarovar, and this ancient beri (Zizyphus tree) marks the spot where Baba Buddha sat with his tools. Also part of the complex is the seat of the Sikh temporal authority, the Akal Takht, the foundation of which was laid in 1606 by Guru Hargobind, who felt that the Sikh faith required a martial tenor. The ground floor of the Akal Takht was ready by 1774 while the rest of the five-storied edifice was completed during the reign of Maharaja Ranjit Singh. The present building of the Takht is of a more recent vintage as it was rebuilt following its destruction in 1983 during Operation Blue Star.