Whatever the reasons, the Old Kingdom state collapsed around 2200 BC and was succeeded by several competing regional dynasties, each claiming authority over the entire Nile Valley. These are the dynasties numbered VII through X, and to them one might add the Eleventh, a dynasty whose center was the Luxor area of Upper Egypt. About 2000 BC, the kings of the Eleventh Dynasty began to reunite the Nile Valley under their rule, and they are therefore considered the founders of the Middle Kingdom state. But no major works of architecture survive from the First Intermediate Period. Nothing comparable to the monuments of the Old Kingdom was produced by any of the period's dynasties, for none of them possessed sufficient resources to build on the scale achieved by the Old Kingdom rulers.