On the floor of the two caves were two very beautiful mosaics, one of which is now in the Barberini palace, the other, which is in a sadly mutilated condition, still on the floor of the west cave.  The date of these mosaics has been a much discussed question.  Marucchi puts it at the end of the second century A.D., while Delbrueck makes it the early part of the first century B.C., and thinks the mosaics were the gift of Sulla.  Delbrueck does not make his point at all, and Marucchi is carried too far by a desire to establish a connection at Praeneste between Fortuna and Isis.[123] Not to go into a discussion of the date of the Greek lettering which gives the names of the animals portrayed in the finer mosaic, nor the subject of the mosaic itself,[124] the inscription given above[118] should help to settle the date of the mosaic.  Under Claudius, between the years 51 and 54 A.D., a portico was decorated with marble and a coating of marble facing.  That this was a very splendid ornamentation is shown by the fact that it is mentioned so particularly in the inscription.  And if in 54 A.D. marble and marble facing were things so worthy of note, then certainly one hundred and thirty years earlier there was no marble mosaic floor in Praeneste like the one under discussion, which is considered the finest large piece of Roman mosaic in existence.  And it was fifty years later than the date Delbrueck wishes to assign to this mosaic, before marble began to be used in any great profusion in Rome, and at this time Praeneste was not in advance of Rome.  The mosaic, therefore, undoubtedly dates from about the time of Hadrian, and was probably a gift to the city when he built himself a villa below the town.[125]

Finally, a word with regard to the aerarium.  This is under the temple of Fortuna, but is not built with any regard to the facade of the temple above.  The inscription on the back wall of the chamber is earlier than the time of Sulla,[126] and the position of this little vault[127] shows that it was a treasury connected with the basilica, indeed its close proximity about makes it part of that building and proves that it was the storehouse for public funds and records.  It occupied a very prominent place, for it was at the upper end of the old forum, directly in front of the Sacra Via that came up past the basilica from the Porta Triumphalis.  The conclusion of the whole matter is that the earliest city forum grew up on the terrace in front of the place where the mysterious lots had leaped out of the living rock.  A basilica was built in a prominent place in the northwest corner of the forum.  Later, another wonderful cave was discovered or made, and at such a distance from the first one that a temple in front of it would have a facing on the forum beyond the basilica, and this also gave a space of ground which was leveled off into a terrace above the basilica and the forum, and made into a sacred precinct.  Because the basilica occupied the middle front of the temple property,