catacombs that contained the relics of Saint Agnes, who was martyred as a thirteen-year-old, and which was attached to the ancient basilica of Saint Agnese mid-way along the liturgical north side. The basilica was originally a "funerary hall" rather than a church in the modern sense. Later legend considerably elaborated Constantina's devotion to Saint Agnes, but it now cannot be determined if this was a factor in the choice of location, although in general terms early Christians believed that their souls benefited from being buried close to martyrs, which was almost certainly a major attraction of the funerary hall to those who paid to be buried in it. Attaching an important mausoleum as an annex to a church was a common practice in Rome and can be seen the cases of other Roman churches such as the Mausoleum of Helena (Constantine's mother, not his daughter), which was attached to the basilica of Santi Marcellino e Pietro ad Duas Lauros, now a ruin. Of the original Basilica of St Agnese, only about a third of the main outer wall survives, from the north side and the apse at the eastern end, but at less than the original height. By the 7th-century the basilica had fallen into ruins and was too large to be refurbished, and the current much smaller Basilica of Sant'Agnese fuori le mura was built to replace it, a few metres away. Purpose It was traditionally thought that construction began during the reign of Emperor Constantine I or shortly after, as an early history, the Liber Pontificalis, records that Pope Silvester I (d. 335) baptized Constantina and her paternal aunt in a baptistry built by Constantine there at the same time as the funerary hall. This was assumed to be the structure that survives. But excavations in 1992 discovered an earlier building beneath, and the existing building is now dated to around 350 AD. The structure of Santa Costanza reflects its original function as the mausoleum of one or both Constantine's two daughters, Constantia and Helena, rather than as the church it became much later. The centralized design put "direct physical emphasis on the person or place to be honored" and was popular for mausoleums and places of baptisms at this time. Other early Christian buildings with a similar origin and a circular plan include Split Cathedral, built within Diocletian's Palace as his mausoleum, and the Rotunda of Galerius