Borobudur is the largest Buddhist monument in South-east Asia. Its overall form is that of a mandala (show in plan and section below). Some scholars believe that the site was originally intended as a Hindu temple, but was converted to a Buddhist monument after construction had begun.
The finished temple recreates in minature a microcosm of the Buddhist cosmos. The pathway up the temple spirals around the center so that the pilgrim may view over a kilometer of bas-reliefs depicting events found in Buddhist sutras and in the Buddha's life. The base of the temple is square, perhaps to symbolize the profanity of the earth. As the pilgrim rises, the squareness gives way to circular rings on the upper terraces, symbolizing the heavens. The rings are composed of miniature stupas, each holding a Buddha inside. This level was probably meant to represent the Buddhist world of "formlessness" in which various Buddhas dwell. At the center of the upper platform is a giant empty stupa. It is not known whether the stupa was always empty, but if it was, the stupa's emptiness conveys the symbolism of having arrived at nirvana where the chain of rebirths finally ends.
The form of the temple is rather unique for its age. Several centuries later, similar (but smaller) mandala temples were built in Cambodia and Thailand. Unlike Borobudur, those temples have "Mt. Meru" at the center, not a large stupa. Mt. Meru is the sacred Buddhist mountain that is believed to reach up into the heavens from the earth far below.
Overall site plan (adapted from Buddhist Art and Architecture, listed below)
All images copyright 2003 Marie Schroeder
Fisher, Robert E. Buddhist Art and Architecture
Richards, Peter (ed.) Let's Go: Southeast Asia