City gates

ROME - City Gate
A generic city gate from the 320's, however, there are some features that set this one apart from most. Besides the thre turrets, compared to the more common two, the gate clearly displays doors, where most do not, and what is more unusual the doors are obviously closed.

 Licinius II, AE Reduced Follis, RIC VII Rome 182

ROME - City Walls
Diocletian, AR Argentius, RIC VI Rome 40a

ARLES in GAUL - City Gate
A generic city gate from the 320's, however, there are some features that set this one apart from most. Besides the four turrets, compared to the more common two, the gate clearly displays open doors. 
 
 Crispus, AE Reduced Follis, RIC VII Arles -, LRBC I - (cf 293-4)

CYZICUS in MYSIA - City Gate
A generic city gate from the 320's.

Constantine I, AE Reduced Follis, RIC VII Cyzicus 51

EMERITA in HISPANIA - City Gate and walls
The prominent feature is the city gate at Emerita, a doube doorway with two tall towers. The city walls are represented by the arch appearing to connect the two towers. Emerita was a colonia built originally for the veterans of the 5th and 10th legions at the close of the Cantabrian wars.

Tiberius, AE 26mm, RPC I 42

LONDON in BRITANNIA - City Gate
The first coin illustrating the city gates at Londinium is a rather special piece. It is on a gold medallion of  five aurei that was struck at the mint of Trier to commemorate the retaking of Britain by Constantius I following the revolt of Carausius and the subsequent defeat of his successor, Allectus. The medal shows the victorious Constantius on horseback approaching the gates of London with an inhabitant of the city welcoming him. LON under inhabitant leaves us in no doubt about the location. 

The reverse legend, REDITOR LVCIS AETERNAE (Restorer of the eternal light), and indeed the whole scene echoes the contemporary account in the Panegyric to Constantius:

"You were the avenger, the liberator long prayed-for, and the moment you reached the shore, a triumphant procession met Your Majesty as you deserved; the Britons, jumping for joy, with their wives and children presented themselves, not merely falling down to worship you yourself, whom they regarded as come down from heaven, but even the sails and the oars of that ship which had brought to them your divinity, and they were quite ready to throw themselves upon the ground and thus feel your coming. And no wonder they were elated with such joy, if, after that helpless captivity of theirs for so many years, after the outrages committed upon their wives, after the degrading servitude of their children they were at length free, at length Roman, at length refreshed by the true light of the empire."

Constantius I, AV medallion of five aurei (electrotype), RIC VI Trier 34

The remaining campgates from London are from the 320's and feature the generic design that occurs so often on Roman coins of this period. All the London ones have no doors and two turrets with a star between.
 
 Constantine I, AE Follis, RIC VII London 293

 Crispus, AE Follis, RIC VII 295

 Constantine II, AE Follis, RIC VII London 296

Constantine II, AE Follis, RIC VII London 296 note

 Constantius II, AE Follis, RIC VII London 298

PRUSIAS AD HYPIUM in BITHYNIA - City Gate
Prusias ad Hypium is a site located, as the name suggests, on the River Hypium. The city gate featured on the coins of Gallienus features two towers that have subsidiary gates to the main one in the centre of the structure. Running along the top there looks to be a row of decoration, perhaps windows.

 Gallienus, AE 8 Assarion, Rec Gen 78

TRIER in GAUL - City Gate
One of the most famous Roman city gates, the Porta Nigra, can be found in Trier. The coins below are generic City Gates of the two turret variety from the 320's. They in no way try to capture the likeness of the Porta Nigra, sadly.
 Constantine I, AE Reduced Follis, RIC VII Trier 504

 Constantine I, AE Reduced Follis, RIC VII Trier 504

TICINUM in GALLIA TRANSPADANA - City Gate
Constantius II, AE Reduced Follis, RIC VII Ticinum 201