| Castlebar to Opwijk | 601.22 mi (967.58 km) |
| Castlebar to Ostend | 543.89 mi (875.31 km) |
| Castlebar to Oud-Heverlee | 624.21 mi (1,004.57 km) |
| Castlebar to Oud-Turnhout | 623.52 mi (1,003.46 km) |
| Castlebar to Oudenaarde | 581.69 mi (936.14 km) |
| Castlebar to Oudenburg | 548.28 mi (882.38 km) |
| Castlebar to Oupeye | 666.54 mi (1,072.70 km) |
| Castlebar to Overijse | 620.41 mi (998.46 km) |
| Castlebar to Overpelt | 643.48 mi (1,035.58 km) |
| Castlebar to Paal | 638.48 mi (1,027.54 km) |
| Castlebar to Peer | 647.17 mi (1,041.52 km) |
| Castlebar to Pepinster | 677.59 mi (1,090.47 km) |
| Castlebar to Peruwelz | 591.48 mi (951.90 km) |
| Castlebar to Perwez | 636.29 mi (1,024.01 km) |
| Castlebar to Philippeville | 639.37 mi (1,028.97 km) |
