| Castleton to Orbetello | 984.77 mi (1,584.83 km) |
| Castleton to Oria | 1,290.80 mi (2,077.34 km) |
| Castleton to Oristano | 1,071.42 mi (1,724.29 km) |
| Castleton to Orta Nova | 1,183.34 mi (1,904.41 km) |
| Castleton to Orte | 1,017.85 mi (1,638.07 km) |
| Castleton to Ortona | 1,086.22 mi (1,748.10 km) |
| Castleton to Orvieto | 995.18 mi (1,601.59 km) |
| Castleton to Orzinuovi | 782.47 mi (1,259.27 km) |
| Castleton to Osimo | 996.26 mi (1,603.32 km) |
| Castleton to Ospitaletto | 778.55 mi (1,252.96 km) |
| Castleton to Ostuni | 1,276.63 mi (2,054.54 km) |
| Castleton to Ottaviano | 1,171.24 mi (1,884.94 km) |
| Castleton to Ovada | 786.85 mi (1,266.31 km) |
| Castleton to Ozieri | 1,038.36 mi (1,671.08 km) |
| Castleton to Paceco | 1,285.17 mi (2,068.28 km) |
