What It Is, and Why It Looks Like That
The Lotus Temple is a Bahá'í House of Worship, completed in 1986 to a design by the Iranian-Canadian architect Fariborz Sahba. Twenty-seven free-standing marble petals are arranged in clusters of three to form nine sides, and the nine is not decorative: Bahá'í houses of worship are required to be nine-sided and to admit everyone.
The lotus was chosen because it is sacred in Hinduism, Buddhism and Jainism alike and belongs to none of them exclusively, which is the whole point of the building. The marble is from Penteli in Greece, the same quarry the Parthenon came from.
It is one of the most visited buildings on earth, which is worth knowing before you picture a quiet afternoon.

