Rome, view from the Capitoline Hill to the Arch of Septimius Severus.

Rome, view from the Capitoline Hill to the Arch of Septimius Severus.

The white marble Arch of Septimius Severus (Italian: Arco di Settimio Severo) at the northwest end of the Roman Forum is a triumphal arch dedicated in AD 203 to commemorate the Parthian victories of Emperor Septimius Severus and his two sons, Caracalla and Geta, in the two campaigns against the Parthians of 194/195 and 197-199. It´s close to the foot of the Capitoline Hill.
The arch was raised on a travertine base originally approached by steps from the Forum's ancient level. The central archway, spanned by a richly coffered semicircular vault, has lateral openings to each side archway, a feature copied in many Early Modern triumphal arches. The Arch is about 23 metres in height, 25 metres in width and 11.85 metres deep.
The three archways rest on piers, in front of which are detached composite columns on pedestals. Winged Victories are carved in relief in the spandrels. A staircase in the south pier leads to the top of the monument, on which were statues of the emperor and his two sons in a four-horse chariot (quadriga), accompanied by soldiers.
The Arch stands close to the foot of the Capitoline Hill. A flight of steps originally led to the central opening, as one still does to the Arch of Trajan at Ancona. By the 4th century erosion had raised the level of the Forum so much that a roadway was put through the Arch for the first time. So much debris and silt eroded from the surrounding hills that the arch was embedded to the base of the columns. The damage wrought by wheeled medieval and early modern traffic can still be seen on the column bases, above the bas-reliefs of the socles.

During the Middle Ages repeated flooding of the low-lying Forum washed in so much additional sediment and debris that when Canaletto painted it in 1742, only the upper half of the Arch showed above ground. The well-preserved condition of the Arch owes a good deal to its having been incorporated into the structure of a Christian church, given 1199 by Pope Innocent III to the church of Ss. Sergio and Bacco. Half the Arch belonged to the Cimini family, who are also attributed for the preservation of the structure (Claustrum Cimini). The stronghold included a tower placed on top of the Arch itself. When the church was refounded elsewhere, the arch remained ecclesiastical property and was not demolished for other construction.

The dedicatory inscription on the arch reads:
IMP · CAES · LVCIO · SEPTIMIO · M · FIL · SEVERO · PIO · PERTINACI · AVG · PATRI PATRIAE PARTHICO · ARABICO · ET PARTHICO · ADIABENICO · PONTIFIC · MAXIMO · TRIBUNIC · POTEST · XI · IMP · XI · COS · III · PROCOS · ET IMP · CAES · M · AVRELIO · L · FIL · ANTONINO · AVG · PIO · FELICI · TRIBUNIC · POTEST · VI · COS · PROCOS · (P · P · OPTIMIS · FORTISSIMISQVE · PRINCIPIBUS) OB · REM · PVBLICAM · RESTITVTAM · IMPERIVMQVE · POPVLI · ROMANI · PROPAGATVM · INSIGNIBVS · VIRTVTIBVS · EORVM · DOMI · FORISQVE · S · P · Q · R
Imp(eratori) Caes(ari) Lucio Septimio M(arci) fil(io) Severo Pio Pertinaci Aug(usto) patri patriae Parthico Arabico et Parthico Adiabenico pontific(i) maximo tribunic(ia) potest(ate) XI imp(eratori) XI, co(n)s(uli) III proco(n)s(uli) et imp(eratori) Caes(ari) M(arco) Aurelio L(ucii) fil(io) Antonino Aug(usto) Pio Felici tribunic(ia) potest(ate) VI co(n)s(uli) proco(n)s(uli) (p(atri) p(atriae) optimis fortissimisque principibus) ob rem publicam restitutam imperiumque populi Romani propagatum insignibus virtutibus eorum domi forisque S(enatus) P(opulus) Q(ue) R(omanus).

In English: "To the emperor Caesar Lucius Septimius Severus Pius Pertinax Augustus Parthicus Arabicus Parthicus Adiabenicus, son of Marcus, father of his country, pontifex maximus, in the eleventh year of his tribunician power, in the eleventh year of his rule, consul thrice, and proconsul, and to the emperor Caesar Marcus Aurelius Antoninus Augustus Pius Felix, son of Lucius, in the sixth year of his tribunician power, consul, and proconsul (fathers of their country, the best and bravest emperors), on account of the restored republic and the rule of the Roman people spread by their outstanding virtues at home and abroad, the Senate and the People of Rome (sc. dedicate this monument)"

Septimius Severus was ruling jointly as emperor with his son Caracalla (Marcus Aurelius Antoninus) when the arch was dedicated. The parenthesized section in the middle is text that replaced an original reference to his other son Geta, which was chiseled out upon Geta's damnatio memoriae by Caracalla.

more on https://en.wikipedia.org/wiki/Capitoline_Hill , https://en.wikipedia.org/wiki/Roman_Forum , https://en.wikipedia.org/wiki/Arch_of_Septimius_Severus

picture generously provided by Rudolf Kaufmann (2015)