| Horley to Orbetello | 806.91 mi (1,298.59 km) |
| Horley to Oria | 1,125.43 mi (1,811.20 km) |
| Horley to Oristano | 885.12 mi (1,424.47 km) |
| Horley to Orta Nova | 1,015.09 mi (1,633.63 km) |
| Horley to Orte | 843.39 mi (1,357.30 km) |
| Horley to Ortona | 917.56 mi (1,476.66 km) |
| Horley to Orvieto | 820.72 mi (1,320.81 km) |
| Horley to Orzinuovi | 611.40 mi (983.96 km) |
| Horley to Osimo | 829.14 mi (1,334.38 km) |
| Horley to Ospitaletto | 608.87 mi (979.88 km) |
| Horley to Ostuni | 1,111.91 mi (1,789.44 km) |
| Horley to Ottaviano | 997.97 mi (1,606.08 km) |
| Horley to Ovada | 607.99 mi (978.47 km) |
| Horley to Ozieri | 852.95 mi (1,372.69 km) |
| Horley to Paceco | 1,102.29 mi (1,773.97 km) |
