They had technology we had to rediscover after the Dark Ages. The Romans has sophisticated machinery and engineers........................
They were no slouches, that's for sure. The obelisk that stands in St. Peter's Square is 25 meters tall and weighs something like 320 tons. People are justifiably amazed by what the Egyptians were able to do with huge stones, but no one seems interested in the fact that the Romans moved that huge obelisk first to Alexandria and later shipped it to Rome, where they positioned it in what became known as the Circus of Nero. In the 1500s, the Italians decided to move and the obelisk to St. Peter's, 250 meters away; it took a titanic effort and nearly failed.