The height of the hill is estimated at 1,000 feet, and it contains two distinct series of caves. The first series is on the "ground floor" and is known as _Simud Hitam_, or "black entrance." The magnificent porch, 250 feet high and 100 broad, which gives admittance to this series, is on a level with the river bank, and, on entering, you find yourself in a spacious and lofty chamber well lighted from above by a large open space, through which can be seen the entrance to the upper set of caves, some 400 to 500 feet up the hill side. In this chamber is a large deposit of guano, formed principally by the myriads of bats inhabiting the caves in joint occupancy with the edible-nest-forming swifts. Passing through this first chamber and turning a little to the right you come to a porch leading into an extensive cave, which extends under the upper series. This cave is filled half way up to its roof, with an enormous deposit of guano, which has been estimated to be 40 to 50 feet in depth. How far the cave extends has not been ascertained, as its exploration, until some of the deposit is removed, would not be an easy task, for the explorer would be compelled to walk along on the top of the guano, which in some places is so soft that you sink in it almost up to your waist. My friend Mr. C. A. BAMPFYLDE, in whose company I first visited Gomanton, and who, as "Commissioner of Birds-nest Caves," drew up a very interesting report on them, informed me that, though he had found it impossible to explore right to the end, he had been a long way in and was confident that the cave was of very large size. To reach the upper series of caves, you leave Simud Hitam and clamber up the hill side--a steep but not difficult climb, as the jagged limestone affords sure footing. The entrance to this series, known as _Simud Putih_, or "white entrance," is estimated to be at an elevation of 300 feet above sea level, and the porch by which you enter them is about 30 feet high by about 50 wide. The floor slopes steeply downwards and brings you into an enormous cave, with smaller ones leading off it, all known to the nest collectors by their different native names. You soon come to a large black hole, which has never been explored, but which is said to communicate with the large guano cave below, which has been already described. Passing on, you enter a dome-like cave, the height of the roof or ceiling of which has been estimated at 800 feet, but for the accuracy of this guess I cannot vouch. The average height of the cave before the domed portion is reached is supposed to be about 150 feet, and Mr. BAMPFYLDE estimates the total length, from the entrance to the furthest point, at a fifth of a mile. The Simud Putih series are badly lighted, there being only a few "holes" in the roof of the dome, so that torches or lights of some kind are required. There are large deposits of guano in these caves also, which could be easily worked by lowering