There is an interesting coin from Constantinople with a bridge on the reverse. This coin was struck to commemorate the dedication of the city in A.D. 330. There was another POP ROMANVS with a star reverse struck at the same time. Some think that the star reverse represents Constantinople and the bridge reverse represents the city of Rome, like the earlier VRBS ROMA and CONSTANTINOPOLIS issues. The big difference is that the POP ROMANVS series was only struck at the mint of Constantinople; so there is no real reason to believe that Rome is alluded to by the bridge reverse.
Many people reference this coin as commemorating the Battle of the Milvian bridge, but that does not seem likely. Primarily because the battle, which occurred in A.D. 312, took place 18 years before the issue of this coin, with no Milvian bridge coin issues struck in between...not a single coin. If this was such an important event it seems that there would have been some coins issued commemorating this bridge earlier. A coin struck this late after an event would not even be recognized by many Roman people.
I believe it is just a generic representation of a bridge, which were crowning achievements of Roman engineering. There was also, quite a large bridge built around this time. Perhaps the POP ROMANVS is alluding to the bridge built over the Danube circa A.D. 328, or just commemorating Roman ingenuity.
The bridge linking the banks of the Danube was an engineering marvel and mentioned in several sources-
Aurelius Victor was a historian who lived circa A.D. 320- 390. He mentioned the bridge in De Caesaribus 13.4 and 41.13. This bridge probably marked the start of a Gothic campaign. Victor said that the bridge was built and then, "camps and forts were strategically placed in many locations."
"Constantine the pious crossed the Danube very many times, and made a bridge for it in stone." Chronicon Paschale
This bridge was even commemorated on a bronze medallion issued in Rome.
So from the primary accounts and the issue of a medallion, it seems that the building of a bridge over the Danube was a big event.
The POP ROMANVS coins were mistakenly included in RIC VIII because when RIC VII was published, numismatists believed that these coins were struck circa A.D. 340, however the Llanbethery Hoard of Constantinian coins, which had one example, helped to prove that these coins were struck earlier.
