| Slough to Orbetello | 835.87 mi (1,345.21 km) |
| Slough to Oria | 1,153.25 mi (1,855.97 km) |
| Slough to Oristano | 914.24 mi (1,471.33 km) |
| Slough to Orta Nova | 1,043.19 mi (1,678.86 km) |
| Slough to Orte | 872.07 mi (1,403.45 km) |
| Slough to Ortona | 945.67 mi (1,521.91 km) |
| Slough to Orvieto | 849.39 mi (1,366.96 km) |
| Slough to Orzinuovi | 639.65 mi (1,029.41 km) |
| Slough to Osimo | 857.05 mi (1,379.30 km) |
| Slough to Ospitaletto | 636.95 mi (1,025.08 km) |
| Slough to Ostuni | 1,139.65 mi (1,834.09 km) |
| Slough to Ottaviano | 1,026.57 mi (1,652.11 km) |
| Slough to Ovada | 637.00 mi (1,025.15 km) |
| Slough to Ozieri | 882.17 mi (1,419.72 km) |
| Slough to Paceco | 1,131.55 mi (1,821.05 km) |
