So called from the beautiful mosaic set _in the wall on the right in entering_, mentioned by Pliny as the work of Sosus existing at Pergamos,--"There is a dove greatly admired in the act of drinking, and throwing the shadow of its head upon the water, while other birds are to be seen sunning and pluming themselves on the margin of a drinking bowl." It was found in Hadrian's Villa. Beyond is also a mosaic representing two scenic masks, found on the Aventine. In the windows are glass cases containing styli, coins, and lamps. 83. Fixed on the side of the farther window, the Iliac Table representing the Fall of Troy as described by Virgil; to each group is attached an explanatory inscription in Greek: found at Bovillæ. 49. Diana of Ephesus. 37. Sarcophagus of Gerontia, representing the fable of Endymion. 13. The Prometheus sarcophagus. On shelves round the room are placed numerous busts, but these are not of much interest. _On coming out of the Museum_ cross the square and turn to the left, by the side of the Tabularium (note the paving-stones at the end of the Sacra Via), then turn to the right, Via Monte Tarpeia, proceed along this street, and keep straight on down the steps. THE TRAITORS' LEAP. By descending the _Centum Gradus_, and turning to the left, we see the rock, within the space closed off by the rails. The house on the top will roughly represent the original height of the rock. If we then add forty feet to the depth, we shall have some idea of the traitors' leap, which cured all ambition. THE TEMPLE OF OPS.