| Harpenden to Opwijk | 204.15 mi (328.55 km) |
| Harpenden to Ostend | 146.46 mi (235.71 km) |
| Harpenden to Oud-Heverlee | 227.07 mi (365.43 km) |
| Harpenden to Oud-Turnhout | 231.70 mi (372.89 km) |
| Harpenden to Oudenaarde | 183.22 mi (294.86 km) |
| Harpenden to Oudenburg | 150.69 mi (242.51 km) |
| Harpenden to Oupeye | 270.22 mi (434.87 km) |
| Harpenden to Overijse | 222.78 mi (358.52 km) |
| Harpenden to Overpelt | 251.42 mi (404.63 km) |
| Harpenden to Paal | 243.95 mi (392.61 km) |
| Harpenden to Peer | 254.23 mi (409.14 km) |
| Harpenden to Pepinster | 280.66 mi (451.68 km) |
| Harpenden to Peruwelz | 192.71 mi (310.14 km) |
| Harpenden to Perwez | 238.27 mi (383.46 km) |
| Harpenden to Philippeville | 240.58 mi (387.18 km) |
