The next wave of monastic reform came with the Cistercian Movement. The first Cistercian abbey was founded in 1098, at Cîteaux Abbey. The keynote of Cistercian life was a return to a literal observance of the Benedictine rule, rejecting the developments of the Benedictines. The most striking feature in the reform was the return to manual labour, and especially to field-work. Inspired by Bernard of Clairvaux, the primary builder of the Cistercians, they became the main force of technological diffusion in medieval Europe. By the end of the 12th century, the Cistercian houses numbered 500, and at its height in the 15th century the order claimed to have close to 750 houses. Most of these were built in wilderness areas, and played a major part in bringing such isolated parts of Europe into economic cultivation.