| Monte Porzio Catone to Oerlinghausen | 726.60 mi (1,169.36 km) |
| Monte Porzio Catone to Oestrich-Winkel | 608.87 mi (979.89 km) |
| Monte Porzio Catone to Offenburg | 514.97 mi (828.77 km) |
| Monte Porzio Catone to Oftersheim | 558.63 mi (899.03 km) |
| Monte Porzio Catone to Ohrdruf | 629.72 mi (1,013.44 km) |
| Monte Porzio Catone to Ohringen | 533.25 mi (858.19 km) |
| Monte Porzio Catone to Olbernhau | 612.18 mi (985.21 km) |
| Monte Porzio Catone to Olching | 446.29 mi (718.24 km) |
| Monte Porzio Catone to Oldenburg | 809.97 mi (1,303.52 km) |
| Monte Porzio Catone to Oldenburg in Holstein | 866.58 mi (1,394.63 km) |
| Monte Porzio Catone to Olfen | 728.61 mi (1,172.59 km) |
| Monte Porzio Catone to Olpe | 676.50 mi (1,088.72 km) |
| Monte Porzio Catone to Olsberg | 688.38 mi (1,107.84 km) |
| Monte Porzio Catone to Oranienburg | 756.11 mi (1,216.84 km) |
| Monte Porzio Catone to Ortenberg | 615.33 mi (990.28 km) |
