The Jews were first shut up within the walls of the Ghetto by the fanatical Dominican pope, Paul IV. (Gio. Pietro Caraffa, 1555--59), and commanded never to appear outside it, unless the men were in yellow hats, or the women in yellow veils. "For," says the Bull Cum Nimis,
"It is most absurd and unsuitable that the Jews, whose own crime has plunged them into everlasting slavery, under the plea that Christian magnanimity allows them, should presume to dwell and mix with Christians, not bearing any mark of distinction, and should have Christian servants, yea, even buy houses."
The Ghetto, or Vicus Judæorum, as it was at first called, was shut in by walls which reached from the Ponte Quattro Capi to the Piazza del Pianto, or "Place of Weeping," whose name bears witness to the grief of the people on the 26th July, 1556, when they were first forced into their prison-house.
"Those Jews who were shut up in the Ghetto were placed in possession of the dwellings of others. The houses in that quarter were the property of Romans, and some of them were inhabited by families of consideration, such as the Boccapaduli. When these removed they remained the proprietors and the Jews only tenants. But as they were to live for ever in these streets, it was necessary that the Jews should have a perpetual lease to defend them against a twofold danger,--negligence on the part of the owner to announce to his Jewish tenant when his possession expired, or bankruptcy if the owner raised his rent. Thus originated a law which established that the Romans should remain in possession of the dwellings let to the Jews, but that the latter should hold the houses in fee farm; that is, the expiration of the contract cannot be announced to a Jewish tenant, and so long as he pays the lawful rent, the rent can never be raised; the Jew at the same time may alter or enlarge his house as he chooses. This still existing privilege is called the Jus Gazzaga. By virtue of it a Jew is in hereditary possession of the lease, and can sell it to his relations or others, and to the present day it is a costly fortune to be in possession of a Jus Gazzaga, or a hereditary lease. Highly extolled is the Jewish maiden who brings her bridegroom such a dowry. Through this salutary law the Jew became possessed of a home, which to some extent he may call his own."--_Gregorovius._