| Harrow to Orbetello | 832.09 mi (1,339.12 km) |
| Harrow to Oria | 1,147.62 mi (1,846.92 km) |
| Harrow to Oristano | 913.17 mi (1,469.60 km) |
| Harrow to Orta Nova | 1,037.91 mi (1,670.36 km) |
| Harrow to Orte | 867.67 mi (1,396.37 km) |
| Harrow to Ortona | 940.42 mi (1,513.46 km) |
| Harrow to Orvieto | 844.98 mi (1,359.87 km) |
| Harrow to Orzinuovi | 634.61 mi (1,021.31 km) |
| Harrow to Osimo | 851.57 mi (1,370.47 km) |
| Harrow to Ospitaletto | 631.71 mi (1,016.64 km) |
| Harrow to Ostuni | 1,133.95 mi (1,824.91 km) |
| Harrow to Ottaviano | 1,022.01 mi (1,644.77 km) |
| Harrow to Ovada | 633.35 mi (1,019.28 km) |
| Harrow to Ozieri | 880.58 mi (1,417.15 km) |
| Harrow to Paceco | 1,129.03 mi (1,817.00 km) |
