| Hertford to Orbetello | 834.54 mi (1,343.07 km) |
| Hertford to Oria | 1,146.74 mi (1,845.51 km) |
| Hertford to Oristano | 919.92 mi (1,480.46 km) |
| Hertford to Orta Nova | 1,037.68 mi (1,669.98 km) |
| Hertford to Orte | 869.05 mi (1,398.60 km) |
| Hertford to Ortona | 940.27 mi (1,513.21 km) |
| Hertford to Orvieto | 846.37 mi (1,362.10 km) |
| Hertford to Orzinuovi | 634.99 mi (1,021.92 km) |
| Hertford to Osimo | 851.02 mi (1,369.58 km) |
| Hertford to Ospitaletto | 631.73 mi (1,016.67 km) |
| Hertford to Ostuni | 1,132.92 mi (1,823.26 km) |
| Hertford to Ottaviano | 1,023.08 mi (1,646.49 km) |
| Hertford to Ovada | 636.15 mi (1,023.78 km) |
| Hertford to Ozieri | 886.54 mi (1,426.75 km) |
| Hertford to Paceco | 1,133.49 mi (1,824.17 km) |
