Places of worship have existed from very ancient times. A Hindu temple, though a place of worship, is much more than that. It is a replica of the universe, an image of God, an image of man with God in his heart—all rolled into one.
The most essential part of a temple is the garbhagṛha or sanctum sanctorum. It is here that the image or the symbol of the deity is installed.
In front of this garbhagṛha, separated from it, will be a big hall (at least in the big temples) known as maṇṭapa or nṛtta-maṇṭapa or navaraṅga. It is used for congregational religious purposes like singing, dancing, recitation of religious texts or religious discourses.
This maṇṭapa can have walls or it can be just a shelter without walls, the roof being supported on pillars. In the latter case it is termed ākāśamaṇḍapa.