Borgo
Set between the Tiber River and Vatican City, Borgo is anchored by Castel Sant'Angelo. Originally Hadrian's tomb, then later a fortress, a papal palace and a prison, the castle is now a museum with sweeping city views from its roof terrace. Wide Via della Conciliazione is lined with food and souvenir vendors as it leads to the Piazza San Pietro. Side streets offer hotels and restaurants catering to Vatican tourists.