Rising like a massive headland above the Tiber, the Aventine Hill is the one area in Rome where trills of birdsong win out over the din of traffic. That's highly appropriate, as the hill's name derives from the Latin avis, the swallows here having once featured in the bird-watching contest whereby Romulus and Remus decided the best site on which to build their city. As it happened, the Aventine lost out to the Palatine. Still, to Romans, the Aventine is known as the most "poetic" of the city's seven hills, D'Annunzio and other poets long having sung its praises. Scented here with roses (from the Roseto Comunale), there with orange blossom (from the Giardino dei Aranci), and everywhere with pines, it seems the opposite of urban: Rome's most idyllic oasis of calm.

This is a rarefied district, where some houses still have their own bell towers and private gardens are called "parks," without exaggeration. Like the emperors of old on the Palatine, the fortunate residents here look out over the Circus Maximus and the river, winding its way far below. And today's travelers still enjoy the great views, including the famous one spotted through the peculiar keyhole at the gates to the headquarters of the Knights of Malta, which may be the most peered-through in the world—take a look and see why.

At the foot of the Aventine hill to the north, the 1st-century temples to Vesta and Hercules are two of the most complete ancient monuments in the city. They remind us that, under the Republic, this area was home to the "plebs," becoming under the Gracchi a populist stronghold. By Imperial times, however, its tradesman and merchants were displaced by patricians seeking fresh air and space, with grandstand views over the Vallis Murcia, the arena-shaped dip dividing this hill from the Palatine. Sumptuous villas and gardens sprang up, giving Alaric, when the Goths visited the city in 410 AD, a ready supply of plunder. The Aventine never quite recovered from such depredations.

South of the Aventine, there's an entirely different flavor. Blue-collar Testaccio is flat and homely but as lively as it gets; ancient Rome's dockyard has, in the modern age, an up-and-coming arts scene with music and dance clubs that go all night. You'll know you've reached Testaccio when you see its most incongruous landmark, the Piramide, a large marble pyramid built as a nod to the pharaohs in 12 BC as a tomb for a rich merchant. Behind the monument lie the remains of some of the English poets who put the Rome in romantic in the 19th century, in the aptly named, and appropriately scenic, Cimitero degli Inglesi (English Cemetery).