Jean II de Chambes built the Château de Montsoreau in 1455. The building marks the transition from military architecture to architecture for pleasure, as shown by the large windows, the numerous chimneys, and the attention paid to sanitation problems. The castle's central dwelling was built directly on the banks of the Loire. Unusually, two right-angled wings, looking like two square towers framing the main building, were built a few years later, at a time when round towers were usually built. This odd choice prefigures the corner pavilions of classical architecture. A spiral staircase probably existed before the current Renaissance staircase.