| Castricum to Orbetello | 761.72 mi (1,225.87 km) |
| Castricum to Oria | 1,032.57 mi (1,661.76 km) |
| Castricum to Oristano | 893.20 mi (1,437.47 km) |
| Castricum to Orta Nova | 931.69 mi (1,499.41 km) |
| Castricum to Orte | 783.68 mi (1,261.22 km) |
| Castricum to Ortona | 837.09 mi (1,347.17 km) |
| Castricum to Orvieto | 761.65 mi (1,225.76 km) |
| Castricum to Orzinuovi | 548.37 mi (882.52 km) |
| Castricum to Osimo | 746.10 mi (1,200.73 km) |
| Castricum to Ospitaletto | 541.39 mi (871.29 km) |
| Castricum to Ostuni | 1,017.53 mi (1,637.55 km) |
| Castricum to Ottaviano | 930.61 mi (1,497.68 km) |
| Castricum to Ovada | 575.82 mi (926.69 km) |
| Castricum to Ozieri | 851.59 mi (1,370.49 km) |
| Castricum to Paceco | 1,075.45 mi (1,730.76 km) |
