| Castle Rock to Orbetello | 5,512.21 mi (8,871.05 km) |
| Castle Rock to Oria | 5,836.53 mi (9,392.99 km) |
| Castle Rock to Oristano | 5,537.83 mi (8,912.28 km) |
| Castle Rock to Orta Nova | 5,727.04 mi (9,216.78 km) |
| Castle Rock to Orte | 5,553.15 mi (8,936.92 km) |
| Castle Rock to Ortona | 5,629.51 mi (9,059.83 km) |
| Castle Rock to Orvieto | 5,530.59 mi (8,900.62 km) |
| Castle Rock to Orzinuovi | 5,323.37 mi (8,567.13 km) |
| Castle Rock to Osimo | 5,540.73 mi (8,916.94 km) |
| Castle Rock to Ospitaletto | 5,320.80 mi (8,563.00 km) |
| Castle Rock to Ostuni | 5,822.64 mi (9,370.63 km) |
| Castle Rock to Ottaviano | 5,708.16 mi (9,186.40 km) |
| Castle Rock to Ovada | 5,314.12 mi (8,552.25 km) |
| Castle Rock to Ozieri | 5,520.83 mi (8,884.91 km) |
| Castle Rock to Paceco | 5,781.98 mi (9,305.19 km) |
