The erroneously named Temple of Minerva Medica is, in fact, a ruined nymphaeum of Imperial Rome, built in the 4th century. Nymphaeum is a building devoted to the nymphs and often connected to the water supply. The decagonal structure in opus latericium is relatively well preserved, the full dome having collapsed only in 1828. It is surrounded on three sides with other chambers added at a later date. There is no mention of it in ancient literature or inscriptions.
The structure represents a transition in Roman secular architecture between the octagonal dining room of the Domus Aurea and the dome of the Pantheon, in particular, and the architecture of nearby Byzantine churches. The diameter of the hall is about 24 metres, and the height was 33 — important from the structural point of view, especially for the ribs in the dome. In the interior are nine niches, besides the entrance; and above these are ten corresponding round-arched windows. Both the interior and exterior walls were once covered with marble.
References:The Château du Lude is one of the many great châteaux of the Loire Valley in France. Le Lude is the most northerly château of the Loire Valley and one of the last important historic castles in France, still inhabited by the same family for the last 260 years. The château is testimony to four centuries of French architecture, as a stronghold transformed into an elegant house during the Renaissance and the 18th century. The monument is located in the valley of Le Loir. Its gardens have evolved throughout the centuries.