These soon became the favoured haunt of many Romans, and were in reality an enclosed public park. They could in some ways be compared with the garden areas found within older residential squares of London. There were a large number of portico gardens in Rome. Fortunately we are able to reconstruct five of these: The Porticus Pompeii, the Templum Pacis, the Divus Claudius, the Adonaea, and the Porticus Livia. These examples help to give an understanding of the concept, and to see the way they may have been planted.

The first public portico in Rome was the Porticus Pompeii constructed in 55 BC by Pompey the Great, who is thought to have based his design on the Hellenistic theatre complex at Mitylene, in Turkey. As in that example the portico garden was an adjunct to the theatre built by Pompey. It was an area enclosed by covered walkways, portici, designed to give shade from the sun and shelter from rain when the audience retired between performances in the adjoining theatre, an architectural device, described by Vitruvius. The adoption of Hellenistic porticoes to enclose the garden within a peristylium, was perhaps partly motivated by the need to separate the garden from the surrounding streets and buildings, and maps locating the ancient portico gardens of Rome indeed reveal their close proximity to other structures. The porticoes of Pompey's much esteemed garden were united into one entity, and thereafter the term portico was used to indicate an enclosed garden of this type.

The area of Pompey's Portico is today hidden from view under housing, but Propertius describes some of the characteristics of the famous garden. There were shady columns and an "avenue thick-planted with plane-trees rising in trim rows" as well as water features with statues. Fortunately a plan of this important garden can be drawn from relevant surviving fragments of the Severan Forma Urbis, a map of Rome engraved on marble that was once placed on public view by the Templum Pacis in Rome (c. AD 200). Opinions differ on the interpretation of lines and dots within the ancient plan. One version interprets the four centrally aligned rows of squares as representing pollarded plane trees, around two large rectangular water basins. Another interpretations however, visualizes these two features as the site of a nemus duplex, the double grove of trees mentioned by Martial. The squares could then indicate that each group of trees were flanked by a row of statues set on plinths. A series of exedrae, semicircular and rectangular recesses, probably provided seating or scholae on the outer margins of the garden. Fountains are mentioned by Propertius and may have been situated in proximity to larger water features, or they may have been placed to the rear of the theatre facade, as at Perge in Turkey, but any interoperation will have to await confirmation by archaeological means. The Porticus Pompeii may perhaps be a more elaborate version of a Greek-style palaestra, an area in which youths/men would exercise, and in Roman times these were usually found next to a public bath suite. Vitruvius describes their ideal qualities:

"Three of the sides are to be single colonnades; the fourth which has a south aspect is to be double, so that when rain is accompanied by gales, the drops may not reach the inside ... On the other three sides, spacious exedrae are to be planned with seats ... double colonnade walks in the open am to be planned [xysta] ... The xysta ought to be so laid out that there are plantations or groves of plane trees between the two colonnades. Here walks are to be made among the trees with spaces paved with cement..."

The Hectatostylum, a colonnade of 100 columns, is marked on the Severan Marble Map as adjoining Pompey's portico immediately to the north and provides a double colonnade. Planttations could refer to box, which was a feature of "sun warmed Europa", a portico garden mentioned by Martial; or the laurel bushes that adorned the Porticus Vipsania, which Martial was just able to see from his garret window. Alternatively there could be vines grown in trellises, such as protected walkways in the Porticus Liviae. Other sources mention two myrtles in the shrine of Quirinus, and a lotus tree in the precincts of Vulcan. Pliny also reports that "different kinds of trees are kept perpetually dedicated to their own divinities, for instance, the winter-oak to Jove, the bay to Apollo, the olive to Minerva, the myrtle to Venus, the poplar to Hercules..." This could perhaps indicate that each species was planted in different areas within a sacred garden or that plantations of a specific species associated with a particular divinity could be found in, or as a grove outside, their respective temple precinct. Other porticoes may have contained a combination of bushes such as laurel, myrtle and box-trees, which are mentioned in a 500 ft long portico garden proposed by Gordian III (c. AD 238-244). The project did not materialise, but the brief description is useful in comparison with those built earlier. Gordian also intended to have a statue-lined central path leading up to a basilica and bath complex "so that the pleasure-parks and porticoes might not be without some practical use".

The components of the Porticus Pompeii may be compared with later portico gardens, for which it provided a model. This type of garden increasingly became associated with a number of important public buildings, such as theatres, bath complexes, libraries, temples, or they could stand on then own. They became fashionable places in which to stroll or sit, where one could be seen; they also served as a venue for assignations, as revealed by Ovid in his Ars Amatoria.

Farrar, L. [1998] Ancient Roman Gardens, Sutton. pp 180-2