The Geometric Enigma of Small Baths at Hadrian’s Villa: Mixtilinear Plan Design and Complex Roofing Conception

Starting from the late Domitian age, during Nero’s Empire and finally Hadrian’s principate, an increasing technological shift concerning both opus caementicium and centering work made it possible to build cupolas with unprecedented technical solutions both in terms of dimension and shapes (Opper 2008: 112, Moneti 1992: 67-69). In particular, Hadrian’s strain was addressed to the development of innovative domes, attested by the existence of various pavilions in his Tiburtine Villa, as well as perfectly expressed by the well-known episode reported by Cassius Dio, namely concerning the disagreement expressed by Apollodorus of Damascus on the Emperor’s ribbed vault design (Dio 1925). Many researches, focused on Hadrian’s cupolas, agree on the importance of the octagonal hall of the Villa’s Small Baths for its unusual shape and daring structure (De Angelis D’Ossat 1936: 16): the geometry and the constructive knowledge makes it a perfect example which proves how great was the mathematicians influence over the architectural design between the 1st and 2nd century AD.