The Colonna fountain was built to be fed water by the Acqua Vergine - this water source was not simply used to feed Rome's fountains at the time but was also used as a general water supply. This meant that it was difficult to feed a fountain that required the kind of water pressure for high jets. This basically meant that fountain builders of that time had to rely on their design skills to create beautiful fountain structures rather than just making an impact with high plumes of water.

In 1830 it was restored, and had two sets of dolphins, with tails entwined, sculpted by Alessandro Stocchi, and set at either end of the long basin. The central sculpture was then substituted with a smaller sculpture and spray.

The designer of the Colonna fountain, Giacomo della Porta, was skilled in harnessing the existing water supply while still creating beautiful structures. In fact, the Colonna fountain is widely held to be one the most magnificent fountains within the city to this day. The fountain is designed in a hectagon shape and was originally to be used partly as a fountain basin and partly as a standard drinking trough. The two sections are combined by straps bearing decorations of lion heads.

The fountain's large water feature come from two sources - the first, via a vase sculpture in the center of the structure and the second, by two small jets between the vase and the edges of the basin. The vase currently in place is a replacement to the original vase, which was damaged. During the replacement the current architect, Stocchi, also added some decorative touches of dolphins and shells.

The fountain that stands within the Piazza Colonna is also of interest to historians for reasons other than its design. This fountain has long been used as a pilgrim's fountain due to its proximity to the Column of St Paul.