The circular monument known as the “Sepulchre” or the “Tomb,” situated at the northern margins of the complex of Hadrian’s Villa (between Piazza d’Oro and the Inferi), has been the object of cleaning and excavation. The building, which has always remained visible, was reproduced in the Ligorio-Contini plan of 1668 and in the general plan of the villa done by Francesco Piranesi in 1781, plans thanks to which we are knowledgeable about architectural details which are lost today. The structure is accessible through a narrow vaulted door, and is composed by an annular corridor illuminated by small windows and a small central room covered by a dome. Brick stamps of the Hadrianic age (123 – 124 AD) found in situ, fragments of columns of the Doric order, and the presence of a large portion of a curved epistyle, appear to exclude the traditional theory that the building was a funerary monument preexisting the construction of the Villa. The structure must have been rather a pavilion or a chapel equipped with marble columns, at least in one phase, and accessible by means of two stairs, as was possible to see following the investigation. Analysis of the wall system has shown that the monument suffered a radical modification in the course of the late Hadrianic age.