| Castle Rock to Opwijk | 4,870.22 mi (7,837.86 km) |
| Castle Rock to Ostend | 4,816.24 mi (7,750.98 km) |
| Castle Rock to Oud-Heverlee | 4,892.35 mi (7,873.48 km) |
| Castle Rock to Oud-Turnhout | 4,881.68 mi (7,856.30 km) |
| Castle Rock to Oudenaarde | 4,855.54 mi (7,814.24 km) |
| Castle Rock to Oudenburg | 4,820.79 mi (7,758.32 km) |
| Castle Rock to Oupeye | 4,930.64 mi (7,935.10 km) |
| Castle Rock to Overijse | 4,890.05 mi (7,869.78 km) |
| Castle Rock to Overpelt | 4,900.50 mi (7,886.60 km) |
| Castle Rock to Paal | 4,900.24 mi (7,886.17 km) |
| Castle Rock to Peer | 4,905.45 mi (7,894.56 km) |
| Castle Rock to Pepinster | 4,942.77 mi (7,954.62 km) |
| Castle Rock to Peruwelz | 4,869.43 mi (7,836.59 km) |
| Castle Rock to Perwez | 4,906.56 mi (7,896.35 km) |
| Castle Rock to Philippeville | 4,916.27 mi (7,911.97 km) |
