An especially comforting nineteenth-century origin story speculated that Indian mounds were actually built by

An origin story speculates that the Indian mounds were built by an ancient civilization called Adena.

The Adena people are considered an ancient native society. They are classified as Mound Builders. They are believed to have lived in the Ohio River Valley 400 years ago b.c.

Although this is a very old civilization, much research has been done on the Adenas. It is currently known that:

You can find more information about this in the ink below:

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.