However, the chronology of this eleventh dynasty is well attested, its kings are known, and under them Upper and Lower Egypt were once more consolidated into a single state, forming what is known as the Middle Empire. Under the twelfth dynasty, which succeeded it, this Empire bloomed rapidly into one of the greatest and most glorious periods of Egyptian history. The dynasty only lasted for 213 years, under seven kings, whose names were all either Amenemes or Osirtasen; but during their reigns the frontiers of Egypt were extended far to the south, Nubia was incorporated with the Empire, and Egyptian influence extended over the whole Soudan, and perhaps nearly to the equator on the one hand, and over Southern Syria on the other. But the dynasty was still more famous for the arts of peace. One of the greatest works of hydraulic engineering which the world has seen was carried out by Amenemes III., who took advantage of a depression in the desert limestone near the basin of Fayoum, to form a large artificial lake connected with the Nile by canals, tunnelled through rocky ridges and provided with sluices, so as to admit the water when the river rose too high, and let it out when it fell too low, and thus regulate the inundation of a great part of Middle and Lower Egypt, independently of the seasons. Connected with this Lake Moeris was the famous Labyrinth, which Herodotus pronounced to be a greater wonder than even the great Pyramid. It was a vast square building erected on a small plateau on the east side of the lake, constructed of blocks of granite which must have been brought from Syene, with a façade of white limestone; and containing in the interior a vast number of small square chambers and vaults--Herodotus says 3000--each roofed with a single large slab of stone, and connected by narrow passages, so intricate that a stranger entering without a clue would be infallibly lost. The object seems to have been to provide a safe repository for statues of gods and kings and other precious objects. In the centre was a court containing twelve hypostyle chapels, six facing the south and six the north, and at the north angle of the square was a pyramid of brick faced with stone forming the tomb of Amenemes III. In addition to this colossal work, the kings of this dynasty built and restored many of the most famous temples and erected statues and obelisks, among the latter the one now standing at Heliopolis. It was also an age of great literary activity, and the biographies of many of the priests, nobles, and high officers, inscribed on their tombs and recorded in papyri, give us the most minute knowledge of the history and social life of this remote period.