I don't understand what you mean by the term "middle kingdom." In the Tang Dynasty of China, they considered themselves to be the Middle Kingdom because they saw themselves as the center of the earth, if that helps.
The Middle Kingdom (mid-Dynasty 11–Dynasty 13, ca. 2030–1640 B.C.) began when Nebhepetre Mentuhotep II reunited Upper and Lower Egypt, setting the stage for a second great flowering of Egyptian culture. Thebes came into prominence for the first time, serving as capital and artistic center during Dynasty 11. The outstanding monument of this dynasty was Mentuhotep's mortuary complex, loosely modeled on the funerary monuments of his Theban ancestors. Built on a grand scale against the spectacular sheer cliffs of western Thebes, Mentuhotep's complex centered on a terraced temple with pillared porticoes. The masterful design, representing a perfect union of architecture and landscape unique for its time, included painted reliefs of ceremonial scenes and hieroglyphic texts. Carved in a distinctive Theban style also seen in the tombs of Mentuhotep's officials, these now-fragmentary reliefs are among the finest ever produced in Egypt.
At the end of Dynasty 11, the throne passed to a new family with the accession of Amenemhat I, who moved the capital north to Itj-tawy, near modern Lisht. Strongly influenced by the statuary and reliefs from nearby Old Kingdom monuments in the Memphite region, the artists of Dynasty 12 created a new aesthetic style. The distinctive works of this period are a series of royal statues that reflect a subtle change in the Egyptian concept of kingship.
