Latium is the plain around Rome, and the atlas keeps it distinct from Rome because early Roman ritual is best read as one Latin tradition among several rather than as a Roman invention that spread outward.
The Latin communities of the plain shared cults before any of them was subordinate to the city. On the Alban Mount, above the lake at the plain's southern edge, the towns held a common festival of Jupiter Latiaris at which each contributed to a shared sacrifice and received a portion; the ceremony continued for centuries after Rome had absorbed the towns politically, with Roman magistrates presiding over what had been a federal rite. Lavinium, near the coast, held altars used by several communities and a cult of the Penates that Roman tradition treated as the origin of its own household gods.
The grove of Diana at Nemi, on a crater lake in the Alban hills, drew worshippers from across the region and beyond it, and votive deposits there include large numbers of anatomical terracottas offered for healing.
The pattern this shows is worth stating plainly, because it is easy to miss under the weight of later Roman material. Roman religion did not begin as the religion of an empire or even of a city. It began as the local practice of one town in a plain of towns that were doing broadly similar things, and much of what became Roman was Latin first.