Presently the path began to follow the edge of a cliff five or six thousand feet above a river—undoubtedly from its size the Brahmaputra—that galloped and plunged among rocks in the bed of a valley on the left hand. Incredible, enormous mountains leaned against the sky in every direction, suggesting barrenness and storms, but the valley lay golden and green in the sunlight, patched with the vivid green of corn-fields, dotted with grazing cattle and with the dark-brown roofs of villages. It looked like an exceedingly rich valley, and well populated.

After a mile or two of gorgeous vistas the track turned to the right and passed between miles of tumbled ruins, whose limestone blocks, weighing tons apiece, had turned to every imaginable hue of green, gray, brown and yellow. Blue and red flowers were growing in the crevices, and trees had forced themselves between tremendous paving stones that now lay tilted with their edges to the sky. Ommony untied the rope across his breast and sat up to observe the ruins, laying both hands on his thighs to ease their aching; and presently he gasped—forgot the agony.

The track passed between two monolithic columns more enormous than the grandest ones at Thebes, and emerged on the rim of a natural amphitheater, whose terraced sides descended for about two thousand feet to where a torrent of green and white water rushed from a cave-mouth and plunged into a fissure in the limestone opposite. The air was full of the noise of water and the song of birds, intoxicating with the scent of flowers and vivid with their color.

Every terrace was a wilderness of flowers and shade-trees, strewn with bowlders that broke up the regularity, and connected one with another by paths and bridges of natural limestone where streams gushed from the fern-draped rock and fell in cascades to the torrent in the midst. There was an atmosphere of sunlit peace.

Above the topmost terrace, occupying about a third of the circumference, were buildings in the Chinese style; the roofs were carved with dragons and the rear walls appeared to be built into the cliff, which rose for a thousand feet to a sheer wall of crags, whose jagged edges pierced the sky.

There were no human beings in evidence, but smoke was rising from several of the buildings, which all had an air of being lived in. The track, which was paved now with limestone flags, led under an arch in the midst of the largest building. The arch turned out to be the opening of a tunnel, twenty feet high at lowest and as many wide, that pierced the mountain for more than a hundred yards, making two sharp turns where it crossed caverns and followed natural fissures in the limestone before it emerged on the edge of a sheer ravine, overlooking another valley that appeared to approach the gorge of the Brahmaputra at an angle of nearly forty-five.

Away in the distance, like a roaring curtain, emerald green and diamond white, blown in the wind, the Tsangpo River, half a mile wide, tumbled down a precipice between two outflung spurs that looked like the legs of a seated giant. The falls were leagues away, and yet their roar came down-wind like the thunder of creation. Below them, incalculably far below the summit, the rising spray formed a dazzling rainbow; and where, below the falls, the Tsangpo became the Brahmaputra, there were rock-staked rapids more than two miles wide that threw columns of white water fifty feet in air, so that the rocks looked like leviathans at war.

The path led up the side of the ravine, curved around a projecting shoulder, and entered another tunnel, which emerged at the end of fifty yards into a natural cavern. There the bearers set the stretcher down and two of them offered to help Ommony up a long flight of steps hewn from the limestone rock. However, he managed to walk unaided and Diana followed him through a great gap in the wall into what was evidently the basement of a building.

There he was met by a brown-robed monk—not an Ahbor, a Tibetan—who smiled but made no remark and led him up winding stairways between thick masonry walls to a gallery that overhung the valley from a height which made the senses reel. It was the upper of two galleries that ran along the face of a building backed against a cliff; doors and small windows opened all the way along it, but the Tibetan led around the far corner, where the wooden planking came to an end at a stone platform and there was one solitary door admitting to a room about thirty feet by twenty, that had a window facing the tremendous Tsango-po Falls.

It was in all respects a comfortable room, with a fireplace at one end and a bright fire burning. On either side of the fireplace there were shelves stacked with European books in several languages. The stone floor was covered with a heavy Chinese rug. There was no glass in the window, but there were heavy shutters to exclude wind and rain, as well as silken Chinese curtains.