Sant'Ercolano di Ostia is a small 19th century mortuary chapel on ancient foundations, next to the cemetery of Borgo di Ostia Antica. which is off the Via di Piana Bella near its junction with the Via di Castel Fusano and due east of the train station.
The revised Roman martyrology 2004 has this:
"5 September. At Porto, SS Acontius, Nonnus, Herculanus and Taurinus, martyrs of an unknown date."
This careful entry does not say that they were martyred together. Rather, they are a collection of early martyrs associated with Porto. The bishop of that place took the relics of SS Herculanus and Taurinus to San Giovanni Calibita in the 9th century, where they remain.
The dedication was given rather arbitrarily to the chapel when it was rebuilt in the 19th century.
This Herculanus has nothing to do with the church of Sant'Ercolano at Perugia.
The history of the building depends almost entirely on archaeological evidence, especially an investigation in 1988-9. However, the excavators reported that the edifice's evolution was very complex and good dating evidence was not found.
The site is at the eastern extremity of the great necropolis occupying the area outside the east gate of the ancient city of Ostia Antica. Here in the 1st or 2nd century was built a funerary enclosure, which has left masonry in the form of opus reticulatum at the bottom of the south wall. The remains include traces of a small columbarium or place for cremation ashes.
This building was allowed to fall into ruin at some stage, but was restored as a putative Christian cemetery church or mausoleum in the 4th or 5th century. The fabric used for the walls back then was salvaged from other buildings, and comprised several cubicula or small enclosures. Several of the graves had the interments covered in tiles laid as a gable (this is called a cappuccina for some reason), indicating poverty.
The excavators discovered subsequent phases of restoration in the north wall, with several strata and a large quantity of human bones.
The ancient city was vulnerable to raids by pirates after the collapse of the Roman Empire and, after a major naval battle between Romans and Muslim pirates from North Africa in 849, it was abandoned and the remaining inhabitants moved to an eastern suburb outside the walls the other side of the necropolis. Pope Gregory IV fortified it, and named it Gregoriopolis but it later borrowed the name of the abandoned city and became Ostia Antica. This causes no end of confusion.
The place functioned as a fortified village until the 19th century, with its own cathedral church of Sant'Aurea a Ostia Antica (which replaced the old city's cathedral basilica). The cemetery chapel was rebuilt in salvaged ancient bricks perhaps in the 11th century, but fell into ruin again at an unknown date.
Until the later 19th century, the countryside around the village was dominated by marshlands and was notorious for malaria. However, archaeological investigations in the ruins of the ancient city had begun in the 1820's. The ruin of the chapel was discernible, and so attracted interest -and, in fact, most of the Christian epigraphs discovered at Ostia were found in its vicinity. This is a hint that this locality had been favoured by the local ancient Christians as their cemetery.
Somebody (who?) had the idea to restore the chapel as a funerary enclosure with an altar, and this was done in 1871. Several archaeologists working in the ancient ruins were subsequently buried here, notably Dante Vaglieri (1913) and Guido Calza (1946).
In 1878, the Italian government began a large-scale project to drain the local marshes and bring them into cultivation. The scheme included a ship canal to Rome, which in the event was left unbuilt. The workers settled in a new village which is now Lido di Ostia, and in 1884 a cemetery was opened for them next to the chapel.
The footprint of the old church is preserved in three zones.
Firstly, there is a small raised courtyard surrounded by a fairly low wall and accessed by five steps leading to a simple portal without a gate. The walls have semi-cylindrical coping stones. This entrance is flanked by a pair of small ancient grey granite columns, obviously brought from elsewhere. The courtyard has beds for shrubs against the walls.
Secondly, there is the funerary enclosure. The external walls of this seem to have been covered in a yellow-painted render, but if so this was removed in the later 20th century. The façade wall retains this covering (this wall is not part of the old church fabric), and contains a large simply molded stone doorcase with metal railing gates. Above, the wall has a cornice into which is inserted a long, thin tablet (now blank) above the doorcase. This in turn is crowned with a small triangular pediment flanked by a pair of simple block acroteria.
The left hand side wall shows the mediaeval brickwork (using scavenged ancient bricks) above the 5th century fabric. There is evidence of a blocked rectangular window. These side walls have tiled coping.
Thirdly, there is the chapel proper which is on a square plan and has a semi-cylindrical apse, also in brick. There is a small round-headed window, high up in the left hand side wall.
The funerary enclosure has tombs and sarcophagi of archaeologists lining its side walls. The yellow render has been left in place on these walls.
The chapel proper is separated from the funerary enclosure by a screen wall (from which the paintwork is falling off) which contains a triumphal arch. The archivolt of this springs from two lengths of cornice running to the corners, at the level of the tops of the side walls of the enclosure. This arch is the chapel entrance, but has no door or gate. It is flanked by a pair of round-headed niches.
The interior of the chapel contains an altar, placed in the small apse. The latter has an arch molding.
Access and liturgy Edit
It needs to be noted that the chapel site is not part of the cemetery, and is outside its walls. So, it is not administered by the city under the Cimiteri Capitolini.
Rather, it is vested in the Soprintendenza per i Beni Archeologici di Ostia. There is no regular opening, but those interested can try to arrange access by appointment. Details of contacts are here.
Much of the exterior can be seen from the street by looking through the fence.
The presence of an altar indicates that the chapel is still consecrated, although apparently no regular liturgies (if any at all) are held here.