Known as Gianicolo in Italian, Janiculum Hill, located west of the Tiber River, is probably your best bet to see the skyline of Rome with enough elevation and perspective to bring out its best qualities. Positioned as the best view of everything Rome, from the domes, obelisks, to the ubiquitous bell towers spurred on every day at noon by the customary cannon firing from Janiculum.
Not considered one of the seven hills upon which Rome was first built, Janiculum will lack the tourist fanfare of more central attraction, which will only serve to make enjoying the view all the better. At the bottom of the hill you'll find a large, ornate fountain (Fontana dell'Acqua Paola) and a couple of lovely churches, while the main attractions atop Janiculum are the statues dedicated to the war hero, Garibaldi. Across the Tiber on the edge of the Trastevere district, Janiculum is a chance to take a deep breath and look over Rome without being overwhelmed by it.