The pyramid of Senusret II () is the funerary monument at El Lahun built for the Egyptian pharaoh Senusret II of the Twelfth Dynasty in the early 19th century BC. The complex centers on a mudbrick pyramid, built atop a yellow limestone outcrop found at the site, that has a ground level base of with sides converging at 42°35′ ± 3′ to the apex high. It was once encased in fine white Tura limestone – which was plundered by Ramesses II in the Nineteenth Dynasty for use in his projects – and capped with a black granite pyramidion. Beneath the pyramid lay pharaoh's funerary chamber. The passages to this substructure had been placed beneath the north chapel adjacent to the pyramid's north face since Djoser built his Step Pyramid in the Third Dynasty, but Senusret II chose to hide it away beneath a princess's tomb, designated 'tomb 10', southeast of the main pyramid to protect his tomb from future grave-robbers. The complex had a small mortuary temple built adjacent the pyramid's east face which was destroyed during Ramesses II's reign, an open causeway which remains unexplored, and a valley temple seemingly disconnected from the rest of the complex owing to its distance from it. The complex was served from a pyramid town called Ḥtp Sn-wsr-t, meaning 'May Senusret be at peace' or 'Senusret is contented', by ancient Egyptians, but is now known as Kahun.
Location and excavation Karl Richard Lepsius visited the pyramid in the 1840s and conducted a brief archaeological survey of the site. Fifty years later, Flinders Petrie conducted the first comprehensive excavations there. A small team led by N. B. Millet of the Royal Ontario Museum and the architect J. E. Knudstad has been working at the site of the pyramid town and pyramid since 1989. They aim to expand upon Petrie's work by re-gathering architectural details of the monuments there, which Petrie had neglected to record in his reports. On 28 June 2019, the pyramid was opened to visitors for the first time since its discovery.
Mortuary complex Main pyramid Senusret II's pyramid was built around and atop a yellow limestone outcrop, approximately high, that the builders used to anchor the core and with the added benefit of reducing construction time and cost. On top of the outcrop, retaining walls were built extending radially outward to the pyramid corners with additional parallel walls spaced between which were then packed with mudbrick. The completed pyramid was encased in fine Tura limestone, which was set into a trench cut into the bedrock intended to prevent a collapse during rainfall, that was plundered in the Nineteenth Dynasty by Ramesses II for his own projects as Petrie discovered from an inscription. It was crowned with a pyramidion of black granite, of which only traces remain.
The pyramid had a base length of approximately at ground level and at the base of the casing trench about below ground level. It converged at an average of 42°35′ ± 3′ towards the apex approximately high. The superstructure was surrounded by a sloped sand-filled trench built to absorb rainwater and protect the substructure from flooding. This trench had a short limestone perimeter wall decorated with deep niches, a reference to the enclosure wall of Djoser's step pyramid.
Substructure Tomb 10 The entry point into an Egyptian pyramid's substructure was always placed on the north side, and had been since Djoser built his step pyramid in the Third Dynasty. This served a religious function by pointing the exit passage towards the circumpolar stars, which the pharaoh joined in the afterlife. Though Sensuret II had a north chapel built, he had the substructure's true entrance hidden-away on the southeast side of the pyramid. This was intended to protect the tomb from thieves, and while Petrie was delayed by months in discovering a passage to the substructure, he found that it had nevertheless been robbed millennia prior. Petrie had Fraser investigate a wide pit that was discovered south of the pyramid's southeast side. This first shaft was used for the burial rites of the king, but was too narrow for use in construction. Instead, a second, larger shaft found further south beneath the floor of a princess's tomb was used for transporting the sarcophagus and building materials into the substructure.
The princess's tomb was accessed from a wide shaft deep. The shaft had a small pit containing an immaculately thrown red pottery bowl and probably also the bones of a calf that were found scattered around the floor. Beyond it lay the tomb's antechamber that was hidden behind a set of fine limestone blocks. It had walls partially of fine white limestone and partially of bare rock with a statue niche carved into the west wall and a pavement that sloped down towards the burial chamber. The burial chamber had walls faced with fine white limestone alongside two adjoining rooms comprising a canopic recess in the east and an offering hall in the northeast. The remains found in the burial chamber included a fragment of a wooden coffin and a green feldspar scarab.
Subterranean passages In the antechamber of 'tomb 10', a collapse in the pavement revealed a secondary shaft that connected on its east to a long north–south oriented corridor which was originally closed off by limestone blocks, but that defence had been circumvented by robbers cutting away the corner wall between the two rooms. The corridor had substantial debris deposits forcing excavators to crawl whilst working in it. It was measured to be long, wide, and high with a vaulted ceiling. It led into a 'lower tomb' or 'entrance chamber', where the entry to the pyramid substructure was originally discovered by way of the narrow shaft. This second shaft connects to the entrance chamber through a small hole raised above the floor of the chamber.
The entrance chamber sits about below ground level, and measured north–south by east–west up to a recessed room containing a deep well. Its walls and ceiling remained bare rock. The well room measured north–south by east–west, while the well itself measured by . The function of the well remains unclear. Petrie made efforts to explore it for further passages, but desisted after draining to a depth of where the determination was made that its base had been reached and that no new chambers existed to be discovered. Thus it may have served simply to monitor the level of groundwater. The well room also contained two recesses carved into its northern wall whose purpose is unknown. These chambers were also a strong source of pottery finds, mainly of Middle Kingdom types though a couple were ascribed to the New Kingdom.
The vaulted corridor then resumes its northward path from the entrance chamber in two sections separated by the 'passage chamber' and terminates at a tall doorway into Senusret II's antechamber. It is inclined at an average of 6°46′ that is shallower in the lower section and steeper in the upper section. The 'passage chamber' is uneven with an average length of north–south and east–west, and was found filled with debris rock from an unknown source. From the chamber, Brunton recovered pottery from various periods including from the Middle Kingdom, Eighteenth and Nineteenth (or later) Dynasties, and the Roman period.
Funerary chambers The antechamber was cut into the rock of the outcrop and faced with fine white limestone blocks. It measures an average of north–south by east–west, with walls tall, and a gabled-roof reaching high. In clearing the chamber, a few fragments of broken pottery and one fragment of an alabaster vessel, all apparently of Twelfth Dynasty worksmanship, were recovered. In the west end is a passage to the burial chamber, the final of which is lined with red granite, rather than limestone. About a fifth of the way through the passage is a second doorway on the south wall with an alternate passage that winds around the burial chamber before entering it at its northeast corner immediately before the sarcophagus. The winding passage may have served a symbolic purpose in allowing the king's spirit to leave his tomb on the north to join the circumpolar stars; but it also isolated the burial chamber like an island, possibly an allusion to Osiris's tomb.
The whole burial chamber with its vaulted ceiling was clad and paved with blocks of red granite and included a red granite sarcophagus near its west wall before which lay an alabaster offering table bearing Senusret II's name. The chamber was oriented east–west measuring along that axis and on the north–south axis. It had walls of variable height about tall and a vaulted ceiling reaching high. It also had two entrances from the east and north. The sarcophagus was exceptionally well made with remarkably minute deviations, but had a pronounced slant towards the south along its length. Petrie remarked that '[t]he sarcophagus is perhaps the finest piece of mechanical work ever executed in such a hard and difficult material'.
The burial chamber has a red granite faced doorway in its south wall that leads via an unclad passage to the offering chamber. The offering chamber measures north–south by east–west, with tall walls, and a vaulted ceiling reaching high. It contains a small niche in its west wall that was apparently cut in the Ramesside period. Despite the precautions taken, the funerary apartments were found looted of most of their contents by Petrie. He found a gold uraeus, probably coming from a statue, which convinced him that the pyramid was the sight of Senusret II's burial. The bones of a human leg, ascribed to Senusret II, were also discovered. One further deviation from standard practice was the displacing of the complex of funerary apartments, particularly the burial chamber, and labyrinth of passages southeast of the pyramid's vertical axis.
Mortuary temple The pyramid had a small mortuary temple on its east side, but it was thoroughly destroyed during Ramesses II's reign preventing a reconstruction of its plan. A considerable number of relief fragments from the temple were recovered, including images of the king, inscriptions of his name, and painted wall chips depicting offerings made. There was also several pieces of red granite bearing carved hieroglyphs painted green that came from the doorways. To the temple's west, a chunk of inscribed grey granite was uncovered that Brunton speculates may have come from an altar originally in the temple. A pair of apparent foundation deposits were also found, one by the temple's southeast corner and another on its east–west axis, that contained pottery that had been arranged in the sand.
Causeway and valley temple The complex had a wide open causeway, but it is unclear whether and how it interfaced with the mortuary temple or the pyramid enclosure, and it remains unexplored. There was also a valley temple, now destroyed, which Dieter Arnold speculates was not connected to the remainder of the complex based on its distance from the site. To the north, lay Senusret II's pyramid town named Ḥtp Sn-wsr-t meaning 'May Senusret be at peace' or 'Senusret is contented', but now known as 'Kahun'.
Subsidiary structures Tomb 7