Pyramids, ancient structures of stone or sometimes brick, resting generally on square bases and tapering upwards with triangular sides, found in different parts of the world, but chiefly in Egypt, where they exist to the number of 70 or 80, and of which the most celebrated are those of Ghizeh, 10 m. W. of Cairo, three in number, viz., the Great Pyramid of Cheop, 449 ft. high, and the sides at base 746 ft. long, that named Chefren, nearly the same size, and that of Mykerinos, not half the height of the other two, but excelling them in beauty of execution. The original object of these structures has been matter of debate, but there seems to be now no doubt that they are sepulchral monuments of kings of Egypt from the first to the twelfth dynasty of them.