The caves of Udayagiri and Khandagiri, called lena in the inscriptions, are essentially dwelling retreats of the Jain ascetics. There are radical differences between the general plans of this group and of the far-famed Buddhist rock-cut monasteries of the Deccan. The latter consist of a congregation-hall surrounded by cells often on three sides and with a verandah or porch on the fourth. But here the hall has been entirely dispensed with: probably the very nature of the religion did not call for it. The cells here open either directly into the verandah or the open space in front.
Another peculiarity of the group is the entire absence of a rock-cut sanctuary, which is an indispensable concomitant of a rock-cut Buddhist establishment. The Jain monks apparently substituted it by a structural one. In later periods, however, some of the dwelling cells were converted into shrines with minor alterations, such as increasing the height of the chamber by the excavation of the floor to a deeper depth and providing greater space by the removal of not only the partition-walls between contiguous cells but those dividing the verandah.
Not laid out on a preconceived plan, the monastic retreats were excavated at different heights. The excavators saved both labour and expense by following the configuration of the rock and connecting different caves, wherever necessary, by rock-cut steps, some of which exist even now. There is a predilection towards excavation near the top of the ledge or boulder, probably to lessen the load over the caves, the rock being of a brittle variety.
Meant for Jain recluses, who are unparalleled for the rigour of their asceticism and extreme self-mortification, the caves provided little amenities. The height of most of the caves, including even the exceptionally large one like Cave-1 ('Rani-gumpha') of Udayagiri, does not allow a man to stand erect; the remaining ones are so narrow that one cannot even stretch oneself. The cells are essentially dormitories, an inference substantiated by a sloping rise of the floor at the rear end to serve the purpose of a pillow. This inclination of the floor extends from one end to the other; evidently each cell was tenanted by a number of monks.
The needs of the residents must have been very few indeed: the walls of the cells were not even provided with niches. To keep scriptures and articles of bare necessity, shelves were often cut across the walls of the verandah. The cells are austerely plain, but their facades and brackets, in important instances, are embellished with carvings. The varied treatment of the cut-out brackets is especially noteworthy.
A fully developed monastery would consist of one or more cells fronted by a common verandah, the latter having, in important instances like Caves 1 (Rani-gumpha), 9 ('Manchapuri' and 'Svargapuri') and 10 ('Ganesa-gumpha') of Udayagiri and Cave-3 ('Ananta-gumpha') of Khandagiri, a levelled ground for courtyard in front. The cells may be ranged on one, two or three sides of the verandah. There is no departure from this general arrangement, even in the double-storeyed caves.
What distinguishes Cave-1 is the addition of two more wings, each in its turn containing a suite of cells with a verandah. The upper storey in most cases does not rest immediately above the lower but recedes back. This devise was due either to the desire to relieve the lower storey of the load of the upper, or to the slope of the rock-face which did not allow enough front space for the upper storey to be perched directly over the lower, or to both.
Coming to the technical details, one cannot but be struck by the similarity between these rock-cut caves and the present-day kachcha houses of eastern India. The excavators evidently attempted to simulate in live rock structural houses with which they were familiar, so that the features peculiar to such structures were reproduced even if they were not required for stability. Thus, the ceilings of the cells are often arched and convex like that of a hut; the roofs of the verandah, supported on non-functional architraves, resting on pillars exactly as in a hut with bamboo or wooden posts, are mostly lower than those of the cells.
The floors of the verandah are at a level lower than those of the cells; the strength of the architraves is seemingly secured by brackets; the roofs of the verandah project outward in the form of eaves, the inner sides of the latter being curved as in a thatched or tiled hut to break the flow of rain-water; the door-jambs sometimes incline inwards, which is inappropriate in masonry or rock.
The number of doors varies from one to four, according to the size of the cells. The doorways are invariably small. Even in cells high enough for a man to stand erect, one has to crawl to enter. The jambs, in some cases, slop inwards, causing the opening slightly wider at the base than at the top, a feature common in many caves of an early date, including the ones at 'Barabar' (District Gaya). The doors have grooves, cut all around their outer frames, probably to receive movable wooden shutters.
Additional holes for hinges at the threshold and the lintel, in a few cases, suggest single doors. Unlike most Buddhist cells, the caves of Udayagiri and Khandagiri are adequately lighted, which is due not only to their general layout but also to the profusion of door-openings. In some rare instances there are windows as well. Patches of shell-lime plaster existing even now indicate that the walls of the caves were at one time plastered here and there.
The Cave Categories
The caves can be divided into two broad categories one plain without a pillared verandah and the other with a regular pillared verandah. Whether this division has any chronological significance or not is difficult to decide, though, on general grounds, some caves of the first category might have been earlier than those of the latter. The former are small, mostly open in the front, and without any architectural pretensions; in a few cases, as in Cave-12 ('Bagh-gumpha') of Udayagiri, the cell-top itself projects to form a verandah.
In the majority of the caves open in the front, a horizontal chase runs above the opening. Whether it is meant to direct rainwater outside the cells or to receive some wooden adjunct is not known. The date of this group is difficult to determine in the absence of any epigraphic evidence.
The interval of time between individual caves of the second category cannot be reckoned in centuries, taking the architectural features as the criterion. Architectonically, they form a homogenous group, with out evincing any appreciable process of development. They are all characterized by a benched verandah; their pillars and pilasters are broadly of the same design- generally square below and above and octagonal in the middle, the corners of the square chamfered with the resultant formation of half-medallions at the points of transition. They have a comparable arrangement of the decoration of the facades with pilasters, arches, railings and mouldings simulating the roofs of structures.
None of them bespeaks a different age or different architecture-tradition. Their architectural features, combined with the paleographic evidence of the inscriptions. A typical verandah-pillar they bear, suggest a date of the 1st century B.C. for all caves of this category, with a probable extension into the next century.