The iconic example of ancient Roman engineering is the Colosseum. It was — and still is — colossal. It was begun in AD 72 during the reign of Emperor Vespasian, when the empire was nearing its peak.

Stepping inside, you can almost hear the roar of ancient Rome. Take a moment to imagine the place in action. Romans filled and emptied the Colosseum’s 50,000 seats as quickly and efficiently as we do our super‑stadiums today.

Canvas awnings were hoisted over the stadium for shade. These passageways underneath the arena were covered by a wooden floor. Between acts, animals and gladiators were shuffled around out of sight.

Ancient Romans, whose taste for violence exceeded even modern America’s, came to the Colosseum for the thrills. Gladiators, criminals, and wild animals fought, providing the public with a festival of gore. For the Colosseum’s grand opening, Romans were treated to the slaughter of 5,000 animals.

By the way, increasingly, must-see sights in a city like Rome can be absolutely mobbed by tourists. But there are often less famous and nearly as rewarding options nearby. For example, you could marvel at just the exterior of the Colosseum…and then be wowed by an easier and less crowded alternative nearby…like the Baths of Caracalla.

The ruins of this massive public bath complex are never crowded and offer a great opportunity to appreciate Roman grandeur and engineering in delightful tranquility.

Public baths were a big deal in ancient Rome. For 300 years, this was a sprawling fitness club and social center complete with a variety of pools, saunas, and cold plunges, like this Olympic-size pool, where Romans of different classes mingled and relaxed in its inviting waters. Inaugurated by Emperor Caracalla around the year 200 — the place was massive. Supplied by its own branch of an aqueduct, the baths could accommodate 1,600 visitors at a time. It was also a chance to enjoy gardens, libraries, and cultural events. Imagine how the brick walls — once veneered with fine marble — supported huge, vaulted ceilings overhead. With delightful mosaic floors, and hundreds of statues in niches surrounding the common person with imperial luxury, this was a place for healthy living and socializing.

There was a parallel world under all this splendor. Imagine, a zone of darkness, heat, and suffering where an army of slaves stoked furnaces. They burned ten tons of wood per day to heat the water…all for the bathing pleasure of the people of Rome.