Two important remains of the oldest times are fortifications of the old Rajagriha town, in Bihar and the fortified capital of Sisupalgarh, perhaps the ancient Kalinganagar, near Bhubaneswar. The Rajagriha fortification wall is made in the roughest possible manner, unhewn stones being piled one on top of the other. This belongs to the 6th-5th century, B.C. However at Sisupalgarh in the 2nd-1st century B.C. stone masons were at work using large blocks of stones to make a very well-made fort entrance that could be closed with huge doors turning on hinges.

We know it for a fact that stone masonry and stone carving were imported in Ashoka's times from Persia. There is abundant evidence of stone masons marks similar to those at Persepolis. However, wood was still the dominant material and in architectural remains of Ashokan times, the gradual transition from wood to stone is apparent. At Pataliputra, remains have been found of a great timber wall that once surrounded the imperial capital, a fact clearly mentioned by Megasthanes who states that everything in his day was built of timber in India.

However, there is one important exception to this and that is the rock-cut architecture of India. We are including a study of cave architecture for the simple reason that the early Indian cave temples and monasteries are masterpieces of "organising space" with beauty and utility in view.

A typical example of early cave architecture is the most datable cave of all, the so-called Lomas Rishi cave in the Barabar Hills of Bihar. An inscription proves that this was excavated for the Ajivika sect in the time of Ashoka himself. The cave carved out of the living rock, measures 55'x22'x20'. The entrance is a representation in stone of a hut entrance, with the end of the roof constructed of bent timber supported by cross beams, the ends of which are shown protruding. A carved frieze of elephants is a stone imitation of similar work in wood along with a stone imitation of trellis work made of small stick of bamboo. This is an excellent example showing the development from earlier shapes in timber translated into stone. The period is the 3rd century B.C.