The first king to start building at Abusir was Userkaf, the founder of the 5th Dynasty, and a man of uncertain origin. He may have been a collateral son of the royal family, a High Priest of Re from Heliopolis, or both.  At Abusir, on a hill some 20 meters high north of Sahure's pyramid, he built a unique structure we refer to today as a sun temple, and which he named "Re's Stronghold" (or possibly "Re's Storage House"). There is only conjecture about his possible motivation for building his sun temple at Abusir. Perhaps there was a royal residence here, or an important sun cult in the nearby Nile Valley. German Egyptologists Werner Kaiser has even suggested that this may have been the southernmost site from which one could see the tip of the obelisk in the temple of Re in Heliopois.

Though Userkaf's pyramid is located at Saqqara, he created the impetus for most of the following 5th Dynasty kings to build their funerary monuments at Abusir. Userkaf's sun temple was excavated by Herbert Ricke and Gerhard Haeny in the mid 1950s. Like Niuserre's complex that followed it, this facility sits atop a promontory on the desert's edge. Userkaf's complex is not only the oldest of these two, but was the first of any built.. If there is a precedence to his temple, it might be the 4th Dynasty Great Sphinx Temple at Giza, which appears to haven been dedicated to the sun god and may have involved ritualistic activity similar to that carried out in the 5th Dynasty sun temples. Unfortunately, Userkaf's sun temple is in a much more ruined state then Niuserre's complex. Furthermore, because of this king's short reign, it was not finished during his lifetime. 

In some respects, sun temples resemble pyramid complexes, because they have a valley temple on the edge of the desert, a causeway and a temple erected on a hill. However, the design of the complex of building making up the sun temple differs completely in both overall conception and detailed execution. Most significant perhaps is the building orientation. While the upper temple with the obelisk is precisely oriented in an east-west direction, the other elopements were not oriented by the cardinal points at all.

Though predating it, Userkaf's sun temple had the same components as Niuserre's sun temple, including a valley temple, and upper temple.  However, the valley temple was more complex, and appears to have served multiple purposes because within it were at least five ritual chapels and in front of these was an open sixteen pillared courtyard. To an extent, this is very similar to the courtyard and chapel of many pyramids, where a pillared courtyard sits in front of a chapel with five statue niches. There may have been an entrance hall with annexes, but the ruins were such that this part of the temple could not be determined. 

The valley temple was surrounded on the sides and back by an enclosure wall that opened on its southwest corner into the causeway. Lehner suggests that oxen may have been led into this area from the open area to the northeast and then funneled down the central lane of the causeway to the upper temple.

The causeway was divided into three lanes by low, thin mudbrick walls. The center lane was rather broad, while the two outside lanes were narrow. Curiously, the causeway was offset from the valley temple and both seem to have been oriented towards Heliopolis. This also relates to the 5th Dynasty pyramids at Abusir, several of which together formed a line pointing to Heliopolis, as do the pyramid's at Giza. Ronald Wells believes that the temple may have also been aligned with certain stars that rose from the horizon around 2400 BC. If true, this might also mean that Userkaf's valley temple acted as an astronomical clock for the sacrifices which were made at dawn. 

Archaeologists believe that the upper temple was probably built in stages. Originally it probably had a square ground plan, and very surprising to archaeologists, it most likely had no obelisk at first. Originally, investigators believe it may have had a low building resembling a mastaba in shape that may have supported a wooden column with an image of the sun disc. Here, evidently, there was once an alter accessible by a low staircase. This may have mimicked the structure at Heliopolis at this point in time.

The upper temple apparently went through four more building phases, some beginning before the previous project was completed. This work was not all performed under the direction of Userkaf. Both Neferirkare and Niuserre appear to have added to the temple, if not others. 

In the second phase of construction, we believe that Neferirkare erected a huge red granite obelisk. The pedestal on which the obelisk rested, clad in quartzite and granite, replaced the temple's central mound. It had a winding corridor that led to the roof of the pedestal, and a sacristy.  In phase three, the enclosure and the area around the obelisk were completely rebuilt, with additions of an inner enclosure wall and chambers of limestone that had not been completely dressed by the start of phase four work. In phase four, the exterior surfaces were dressed in plastered mudbrick. 

In phase five, a mudbrick altar was added to the east side of the pedestal, though there were probably altars prior to this. If animals were slaughtered for sacrifice, there was nevertheless no burnt areas on the altar, even though the Palermo Stone mentions that two Oxen and Two Geese were sacrificed daily in Userkaf's sun temple. The altar was surrounded by a curiously diminutive enclosure wall. In front of the altar (east) and to either side of it were stall like niches 

One two sides of the alter, to the north and south, shrines of diorite were built in which there probably stood statues of Re and Hathor, the deities venerated in the sun temple.

To the east (towards the front of the temple) of the alter were five benches, or low tables made of mud and broken stone. Ricke thought they were for setting out offerings, or perhaps benches for priests. Priests and laborers were traditionally organized into five phyles and within one of the benches was found a stele labeled Wer ("great") phyle, which might be compelling evidence that the benches were used by priests.

The sun temple also included magazines, and surrounding everything was a huge enclosure wall with rounded outer corners. It has yet to be established whether the rounded corners

References

Title	Author	Date	Publisher	Reference Number
Complete Temples of Ancient Egypt, The	Wilkinson, Richard H.	2000	Thames and Hudson, Ltd	ISBN 0-500-05100-3
Complete Pyramids, The (Solving the Ancient Mysteries)	Lehner, Mark	1997	Thames and Hudson, Ltd	ISBN 0-500-05084-8
Dictionary of Ancient Egypt, The	Shaw, Ian; Nicholson, Paul	1995	Harry N. Abrams, Inc., Publishers	ISBN 0-8109-3225-3
History of Ancient Egypt, A	Grimal, Nicolas	1988	Blackwell	None Stated
Oxford History of Ancient Egypt, The	Shaw, Ian	2000	Oxford University Press	ISBN 0-19-815034-2