Buddhist religious architecture developed in the South Asia in the third century BC.
Two types of structures are associated with the religious architecture of early Buddhism: viharas and stupas.
Viharas initially were only temporary shelters used by wandering monks during the rainy season, but later were developed to accommodate the growing and increasingly formalised Buddhist monasticism. An existing example is at Nalanda (Bihar). A distinctive type of fortress architecture found in the former and present Buddhist kingdoms of the Himalayas are dzongs.
The initial function of a stupa was the veneration and safe-guarding of the relics of the Buddha. The earliest existing example of a stupa is in Sanchi (Madhya Pradesh). In accordance with changes in religious practice, stupas were gradually incorporated into chaitya-grihas (stupa halls). These reached their highpoint in the first century BC, exemplified by the cave complexes of Ajanta and Ellora (Maharashtra). The Pagoda is an evolution of the Indian stupa.
Buddhist temples were developed rather later and outside South Asia, where Buddhism gradually declined from the 6th/7th century AD onwards, though an early example is that of the Maha Bodhi Temple at Bodh Gaya in Bihar.
Some people complain about the magnitude in size and cost of some temples in Asia and elsewhere, but forget that the great artistic skill is used for a wholesome purpose. The design serves a functional purpose in providing a place for study and meditation for many people and the beauty of the structures is at least a skilful means, for the understanding of Buddhism and the wholesome representation of the teacher and teachings at its best.