| Castel Gandolfo to Oria | 273.16 mi (439.61 km) |
| Castel Gandolfo to Oristano | 247.44 mi (398.21 km) |
| Castel Gandolfo to Orta Nova | 160.81 mi (258.80 km) |
| Castel Gandolfo to Orte | 51.14 mi (82.30 km) |
| Castel Gandolfo to Ortona | 98.89 mi (159.16 km) |
| Castel Gandolfo to Orvieto | 72.61 mi (116.86 km) |
| Castel Gandolfo to Orzinuovi | 286.71 mi (461.42 km) |
| Castel Gandolfo to Osimo | 127.20 mi (204.71 km) |
| Castel Gandolfo to Ospitaletto | 292.97 mi (471.50 km) |
| Castel Gandolfo to Ostuni | 265.57 mi (427.39 km) |
| Castel Gandolfo to Ottaviano | 113.22 mi (182.22 km) |
| Castel Gandolfo to Ovada | 283.91 mi (456.91 km) |
| Castel Gandolfo to Ozieri | 206.04 mi (331.59 km) |
| Castel Gandolfo to Paceco | 260.10 mi (418.58 km) |
| Castel Gandolfo to Pachino | 371.38 mi (597.68 km) |
