| Castaic to Opwijk | 5,588.51 mi (8,993.84 km) |
| Castaic to Ostend | 5,537.06 mi (8,911.04 km) |
| Castaic to Oud-Heverlee | 5,609.83 mi (9,028.15 km) |
| Castaic to Oud-Turnhout | 5,595.42 mi (9,004.96 km) |
| Castaic to Oudenaarde | 5,576.34 mi (8,974.26 km) |
| Castaic to Oudenburg | 5,541.61 mi (8,918.36 km) |
| Castaic to Oupeye | 5,645.62 mi (9,085.74 km) |
| Castaic to Overijse | 5,608.24 mi (9,025.59 km) |
| Castaic to Overpelt | 5,613.39 mi (9,033.87 km) |
| Castaic to Paal | 5,614.92 mi (9,036.34 km) |
| Castaic to Peer | 5,618.68 mi (9,042.39 km) |
| Castaic to Pepinster | 5,657.95 mi (9,105.59 km) |
| Castaic to Peruwelz | 5,592.13 mi (8,999.66 km) |
| Castaic to Perwez | 5,624.72 mi (9,052.11 km) |
| Castaic to Philippeville | 5,637.62 mi (9,072.87 km) |
