Oldau, now a district of the municipality of Hambühren in the Celle district, was first documented in 1378 as "Oldowe." The name is derived from the Old Saxon word "Aue," referring to the fertile, wet river landscape along the Aller River. The village has a long history dating back to the early Middle Ages. Due to its location in a floodplain and proximity to the river, it was already a favored settlement area in prehistoric times.
In the 20th century, Oldau experienced significant changes due to potash mining and industrialization. The Oldau hydroelectric power station was built in 1909/10 and played a central role in the region's energy supply. The Aller canalization, carried out from 1908 to 1919, also shaped the village. The construction of a train station in 1903 better connected Oldau to the surrounding region.
Oldau remained part of the municipality of Oldau until its incorporation on January 1, 1970, and was then incorporated into Hambühren. Today, the village is known primarily for its historic hydroelectric power plant and the charming floodplain landscape surrounding the village.