Erde is currently at the height of its Classical Period, or to put it another way, at the end of its Iron Age. Unlike Earth, all seven of the civilizations have advanced at roughly the same rate, so while some cultures may be more technologically advanced than others, by and large all the innovations currently available, such as they are, are known to all of the cultures. Of course, in a pre-steam, pre-industrial world, the state of the art can look somewhat primitive. Here is an overview of the current level of Erdan technology:
Things people have known for a long time: pottery, basket-weaving, mining, sailing vessels, the wheel, papyrus & ink, clay tablets & styli, glass, padlocks, irrigation, iron smelting, sundials, water clocks, cranks, beer, and wine.
The latest thing: the invention of zero.
Things that have not yet been developed or discovered: blast furnaces, lateen sails, gunpowder, canal locks, parabolic mirrors, printing, spinning wheel, mechanical clocks, distilled spirits, and so on.
Erde is not Earth, so precise parallels are impossible, but generally, if you can’t imagine it in the Roman Empire, it doesn’t yet exist on Erde.
Of course, within these technological constraints, there is a lot that is possible.
Even with only a primitive compass, creative navigation techniques and extant sailing technology allow for long-distance trading.
Water clocks, sundials, and candles can mark the passage of time; calibration is imprecise and accuracy out of reach, but the tools do well enough for the speed of the age.
Long distance communication is also achievable. While most travelers can cover only about 15 miles a day, Hirokoa runners can cover almost 75 miles in a day carrying light messages and Imperial Riders on the Honeycomb Road in the Haan Lands can manage twice that, moving a package across the empire in less than week. Attikan firesignals reach across their territory, conveying messages with great rapidity. Of course, these methods draw enormous amounts of resources and are available only to the ruling classes; even commercial interests cannot access these systems.
Scientific advancement outstrips the buildable and the observable: mathematical calculations and deductive reasoning extend knowledge beyond the merely practical, and prediction of astronomical events, the measurement of great distances, and classification of the natural world are extensive and accurate.