| Potters Bar to Orbetello | 832.78 mi (1,340.22 km) |
| Potters Bar to Oria | 1,146.44 mi (1,845.02 km) |
| Potters Bar to Oristano | 916.33 mi (1,474.69 km) |
| Potters Bar to Orta Nova | 1,037.09 mi (1,669.03 km) |
| Potters Bar to Orte | 867.75 mi (1,396.51 km) |
| Potters Bar to Ortona | 939.64 mi (1,512.20 km) |
| Potters Bar to Orvieto | 845.06 mi (1,360.00 km) |
| Potters Bar to Orzinuovi | 634.11 mi (1,020.50 km) |
| Potters Bar to Osimo | 850.56 mi (1,368.84 km) |
| Potters Bar to Ospitaletto | 631.00 mi (1,015.50 km) |
| Potters Bar to Ostuni | 1,132.68 mi (1,822.88 km) |
| Potters Bar to Ottaviano | 1,021.92 mi (1,644.63 km) |
| Potters Bar to Ovada | 634.22 mi (1,020.68 km) |
| Potters Bar to Ozieri | 883.28 mi (1,421.51 km) |
| Potters Bar to Paceco | 1,130.88 mi (1,819.97 km) |
