The closest is Palazzo dei Papi di Viterbo, 1 km south-west of the city centre; the most famous is Castel Sant'Angelo — #17 of 7,738 worldwide — 65 km south-east. The oldest dated site in the circle is Servian Wall, founded 350 BC.
The 100 km circle reaches into 2 countries — Italy (75), Vatican City (2).











