What were the maya doing by AD 200

The Maya Empire, centered in the tropical lowlands of what is now Guatemala, ... writing, calendar-making and mathematics, and left behind an astonishing amount of ... Most of the great stone cities of the Maya were abandoned by A.D. 900, ...

first, the romans stayed isolated because they had to defend their own territories from neighboring cities that were harassing them, like the etruscans. second, once the romans managed to defeat their neighbors, and started to expand their territory, they started to build roads and bridges. finally, now that the romans have covered their territory with roads functioning as highways, they could mobilize their legions faster to assemble larger military units in a specific place