It was Numa Pompilius who consecrated places for the celebration of religious services, and they were were called argei. Twenty-seven of these shrines were located at various points within the four regions into which Servius Tullius divided Rome when the city did not yet include the Capitoline or the Aventine. Two of these shrines were located on the Viminal hill, one at each end of the ridge. Most shrines were parts of, or within the precincts of, other buildings, but one of them possibly had its own independent building.

After customary sacrifices on March 16-17, the Pontifex Maximus, the flamen dialis and his wife, the Vestal Virgins, the praetor urbanus, and other authorized magistrates went to the shrines in a procession that followed a prescribed route. The nature of the rites at the various shrines is not known except that human figures made of straw were placed there. A second procession took place on May 14, and more is known about the activities on this day. The straw effigies were collected from each shrine as the procession wended its way through the city until it reached the Sublician bridge. There the Vestals finally disposed of them by throwing them into the Tiber. The ceremony was so ancient that Romans themselves did not know what deity was honored or appeased by the rite.

The argei, which refers to both the shrines and the straw figures, are surrounded by disputes as to their exact number, their significance, their origin, and even the dates of the processions. It was likely a great act of purification, regardless of whether the straw figures were substitutes for human sacrifices, whether they numbered 24, 27, or 30, whether they were connected to the Greek Argives or not, and whether the procession in May was on the fourteenth or the fifteenth of the month.

The shrines were solemnly visited on the Liberalia, or festival of Bacchus, and also, they seem to have been the depositories of topographical records.

Here are a few resources for additional information about the shrines of the Argei.