The Mandir is the focal point of the complex. Designed according to the Stapatya-Shastra, a Vedic text that develops Hindu architecture to metaphorically represent the different attributes of God, it is constructed almost entirely from Indian marble, Italian marble and Bulgarian limestone. The stone was shipped to India where it was hand-carved by over 1,500 craftsmen. Each individually numbered piece was then shipped back to London and the building was assembled like a giant three-dimensional jigsaw. The Mandir facility contains no iron or steel, a unique feature for a modern building in the UK. A feature the temple is noted for is its profusely carved cantilevered dome, believed to be the only one in Britain that does not use steel or lead. The Mandir was inaugurated on 20 August 1995 by Pramukh Swami Maharaj, the spiritual leader of BAPS - the organisation behind the temple.
The Mandir serves as the centre of worship. Directly beneath each of the seven pinnacles seen from the outside is a shrine. Each of these seven shrines houses murtis (images) within golden altars. Each murti is treated like the incarnation of Godhead and therefore each deity is bathed, clothed, fed, and attended to each day by the sadhus (monks) who live in the temple.
Beneath the Mandir, is the permanent exhibition 'Understanding Hinduism'. Spread over 3000 square feet, the exhibition deals with the origin, beliefs, glory and contribution of Hindu seers and scholars in the fields of mathematics, astronomy, medicine, education, and religion. The messages and information are presented through visual effects, paintings, tableaux, traditional craftwork, and miniature 3-D dioramas.