One building project that was lost to us, but now is found is the little pavilion built for Senusret I's first jubilee (Sed) festival, which according to custom, occurred during the king's 30th year as ruler (though it is probable that Senusret's festival was held in his 31st year of rule). It was probably built to house the royal barque and is sometimes referred to as a "barque shrine". Popularly known as the White Chapel, it had been disassembled and used as fill in Amenhotep III's Third Pylon at Karnak during the 18th Dynasty. In 1924, the director general of the Egyptian Antiquities Service, Pierre Lacau, ordered his director of works at Karnak, Henri Chevrier, to repair this Pylon, but in order to do so, the pylon had to be dismantled. 

It took years to do so, because it could only be done when the Nile was in a low phase, due to ground water. During this work, Chevrier discovered some 951 blocks that belonged to a total of eleven different structures that had been used as fill within the pylon. While many of the blocks were damaged, their reliefs were often in outstanding condition, due to the layers of mortar which had both bound them together and protected the blocks.

This work progressed slowly, but methodically, and after determining the proper block orientation and placement, Chevrier was able to reconstruct almost completely the so called "White Chapel" of Senusret I and the barque shrine of Amenhotep I. Both buildings are now located in the Open Air Museum at Karnak, along with the Red Chapel of Hatshepsut. The White Chapel as a structure is considered by many to be the most elegant, as well as the oldest structure in Karnak today, and Chevier thought that the structure may have once been covered in gold foil, so it could have been all the more glorious. 

The White Chapel is a small, simple, but eloquent structure, built of Egyptian alabaster (calcite), most notable for its many inscriptions. It was probably built during the remarkable purity of form in this structure is echoed in the austerity of the temple at Qasr el-Sagha. Ramps led up on either side to the small rectangular building, situated on a platform, in which Senusret I himself possibly sat enthroned during part of his Sed festival. There are twelve pillars around the outside of the kiosk, with another four in the interior that support a complete roof. These pillars are decorated with raised reliefs on all four sides. Between the outside pillars is a low, rounded balaustrade. The different nomes of Egypt (the administrative centers) are recorded in columns on the parapet (base). Within the chapel, the god depicted with Senusret I is usually Amun-Re in his guise of the god of procreation and fertility, Min. 

In many of these depictions, the god stands, ithyphallic, on a rectangular pedestal and is swathed as though a mummy, with linen bands crossed over his chest and with two tall feathers attached to the fillet around his head. Long streamers from the head band hang down his back almost to the ground. His right arm is raised behind him holding a flail, the symbol of kingship. In these scenes, we find tall plants behind Amun-Min that depict cos lettuce which, even today as in antiquity, is regarded as a potent aphrodisiac. The plant was associated with Amun-Min. In other scenes, Amun is depicted in similar dress as the king, again with the tall feathers, usually offering the sign of life to the king. Alas, we find the king being led before Amun by Re-Horakhty, who instead offers the king the sign of life. 

In various scenes, the king is shown either wearing the Red Crown of lower Egypt, which interestingly, appears to made of basketry, or the Double Crown of Upper and Lower Egypt.

As an example of the scenes found within this chapel, from a viewpoint inside we see on one of the left central pillars Senusret I, who is offering a ritual conical loaf (shewbread?) to the god, Amun-Min. On the right, the north pillar of the eastern doorway is shown Atum, the Lord of Heliopolis, conducting the king towards Amun-Min, saying to him, "Come in peace, O Senusret, that thou mayest see thy father, Amun Re, who loves thee, that he may give thee the kingship of the Two Lands".  Barely discernible on the shaded face of the pillar, the king is followed by his ka and embraces Amun-Min.

In the center of the scene on the pillar which stands at the north east corner of the building, Senusret I is consecrating to the god the sacred mast which he has erected for him and in return Amun-Min says to him, "I who am thy father, O Senusret...I establish thy crown as King of Upper and Lower Egypt on the throne of Horus, living for ever."

As an interesting side note, the White Chapel provides one of the earliest records of a "river-unit". This is a measurement that appears to correspond to 20,000 cubits in length, or about 10.5 kilometers.

Detail of the Finely Carved Raised Reliefs

However, it is not the content of the inscriptions that set this monument apart from almost all others in Egypt, but it is the minute, carved details of the costumes and glyphs, which were usually not engraved but added in paint.  The reliefs and hieroglyphic inscriptions are integrally related to the architectural design and are not only some of the best work known from the Middle Kingdom, but of all the monuments in Egypt. Their caring and spacing was never really surpassed. 

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