Water is the Reason for its Existence
The Fountain in Piazza d'Ara Coeli
You will find the Ara Coeli fountain in the reasonably quiet square in front of the old townhouse of the noble family of Muti, opposite the bottom of the two splendid staircases that climb side by side, yet contrast completely with each other. One leads to the church of Ara Coeli, high at the top; it is steep and as tiring to scale as it is to win a battle. The other requires no effort and has low, almost lingering steps: a ramp that culminates in the small Capitoline square.
Like almost all the fountains in Rome that are not ostentatious, showy and monumental, ("tourist fountains"), the Ara Coeli fountain is unfamiliar to people who do not know the city; even Romans themselves. You will soon see, if you mention it to them, that they have never heard of it or, at best, they will try to please you by saying, "Oh, yes! Now I understand which fountain you mean" when you know very well that they have not understood at all.
Despite the fact that the fountain at Piazza d'Ara Coeli's shape makes it extremely difficult to examine and get the "feel" of it, the Ara Coeli Roman fountain is one of the few in which the architect has managed to fuse the two elements into a successful whole. On the one hand, there is the receptacle, the architectural style of the basin; on the other, the water it must contain. If you took away the water could you still call this arrangement of pool, balusters, basins and cherubs a fountain? It is the water that unites and gives life to the entire structure; it is the very reason for its existence. Without the water the arrangement would be meaningless.
As for its history, this is more or less exactly the same as that of the side fountains in Piazza Navona. The original design that della Porta handed over in 1589 to the Lombard Andrea Brasca, the Florentine Pietro Gucci and Pace Naldini showed plans for a fountain very different from the one we see now. There was no circular pool around it, but a raised basin repeating the elongated, undulating "boat-shaped" outline of the usual two steps that formed the base. It is almost identical to the pool around the Tureen Fountain.
The base was in turn surrounded by a channel that may have been as deep and wide as the first step, evidently to collect and carry away the water -- not so much the water that had overflowed the edges of the pool, but the water that was made to gush intentionally from the four lion heads on the side of the lower basin. This is the same technique Master Domenico used in the fountain at Montecavallo.
Above the massive marble basin a baluster rests on a cubiform base decorated with festoons. At the top, two small civic crests alternate with two larger ones bearing the arms of Alexander VII Chigi (1655-67) recording the restoration of the Ara Coeli fountain which, however, took place before 1675, since the sketch mentioned above is by Falda.
For the upper part of the Ara Coeli fountain, della Porta was clearly inspired by the ancient fountain in St. Peter's Square, from which he took the idea of the basin with four smiling cherubs (carved by Brasca) pouring water from four little pitchers.
Apart from some minor restoration under Alexander VII, that is more or less the original Ara Coeli fountain. At some later date the whole of the bottom part (the base consisting of two steps and the carved channel) was replaced by the present circular pool and enclosed by the stumpy posts and iron railing.
Obviously, this clever architect had in mind Bernini's alterations to the basins by della Porta in the fountains at Piazza Navona and wanted to achieve something similar here. There is no doubt that he succeeded.