Among the circles. A geometrical analysis of the Teatro Marittimo in Villa Adriana

Among the many architectural achievements of the Roman Emperor Hadrian (76-138 AD), those of Villa Adriana in Tivoli are the most representative. Circular geometries, frequent in Hadrian architecture, are well represented at Villa Adriana. The most attractive and charmingis in the so-called “Teatro Maritimo’. Its circular structureis emphasized by the annular water canal surrounding the ‘isle’, which is accepted as the very place where the Emperorusedto stay when in Villa Adriana (Chiappetta, 2008). For the geometrical analysis of the structure, the plan of M. Ueblacker (Ueblacker, 1985) has been utilized: it emerged as the best among the available surveys. The plan was imported into the CAD (Computer Aided Drawing) application through a calibrated scanner; the analysis was conducted by drawing best-fitting circles on the water canal annulus as well as on the Porticus annulus. The result is that the water canal annulus is interpretable as a 41-58 (x2) CQC geometry(Ranieri, 2009) and the Porticus is consistent with an annulus capable of bearing a regular pentagon inscribed in it. The length-unit derived for both annuli equals the roman foot of 0.296m within few mm, although a shorterunit of 0.291m also appears possible.