In one or two Greek theatres subterranean passages have been discovered, leading from the stage-buildings to the middle of the orchestra. These passages are generally rather more than six feet in height, and from two to three feet wide. There is one in the theatre of Eretria, with a flight of steps leading down to it at each end.[371] Another has been found at Magnesia; but as only a small portion of it still remains, it is impossible to say where it began and where it ended, or whether it had any exit into the orchestra.[372] The passage at Sicyon is rather peculiar. A small drain runs underground from the auditorium to the centre of the orchestra, where it falls into a square tank. From the tank onwards there is a regular vaulted passage, which is continued as far as the back of the stage-buildings, and finally ends in a tunnel in the rock. Where it passes under the stage, a flight of steps leads down to it; but no traces of an entrance from the orchestra can be detected.[373] These three passages, when first discovered, were thought to have some connexion with the dramatic performances; and it was supposed that they might be used to enable ghosts to appear suddenly in the middle of the orchestra. But this theory seems to be untenable, for the following reasons. In the first place, no traces of such passages have been found at Athens, and Epidaurus, and other theatres where excavations have been carried on. But if they had been a regular contrivance in dramatic exhibitions, it is impossible to suppose that the Athenians would not have made use of them. Secondly, the passage at Sicyon not only reaches as far as the stage, but also runs right on to the back of the stage-buildings, where it would have been of no use for the purpose suggested. Thirdly, there is no decisive evidence that the passages at Sicyon and Magnesia opened out into the orchestra. Fourthly, similar passages of Roman workmanship have been discovered at Tralles and at Magnesia, the passage in the latter place having been substituted for the previous Greek one. But these Roman passages had no exit into the orchestra, as the remains clearly show. After running from the stage-buildings to the middle of the orchestra, they branched off to right and left like the letter T, and then stopped.[374] The fact then that the Romans built tunnels of this kind, which had no connexion with performances in the orchestra, is a strong reason for assuming that the Greeks might do the same. What the purpose of the tunnels was, whether Greek or Roman, has not yet been explained, and remains very mysterious.[375] [Illustration: FIG. 8.]