Buildings and monuments as ancient coin types are an interest of mine. Pausanius, writing in the late second century, is a very helpful resource. The Description of Greece is the only extant work of his and is split into ten books. He describes, in detail, the features of the cities and culture of mainland Greece.
His entry for Gythium, the port of Sparta, in Laconia includes this entry:
Book III, 21, 9 "....and the gates (of the city wall) here are called Kastorides (sacred to Castor)"
Reproduced on the coinage for the city we find one particular reverse type that reflects this, the Dioscuri, Castor and Pollux, with their horses, an obvious reference to the city gate.
This is one of a number of reverses that can be linked to features of Gythium referenced in Pausanius. The city only appears to have struck coins during the period 202-205 AD, on the basis of the known portrait styles of Caracalla and Geta, along with the presence of issues of Plautilla. It is not surprising that Gythium adopted the use of local architectural types to express their own civic identity
The reason for the burst of production, not just at Gythium, but all over the Pelopennese, is uncertain. One suggestion is that the local base metal coinage spike because of the tailing off in the production of aes and the favouring of silver from the central mint in Rome necessitating the production of local small denominations to meet the economic needs.
