| Rio Maior to Oerlinghausen | 1,212.22 mi (1,950.87 km) |
| Rio Maior to Oestrich-Winkel | 1,106.88 mi (1,781.35 km) |
| Rio Maior to Offenburg | 1,046.54 mi (1,684.24 km) |
| Rio Maior to Oftersheim | 1,104.42 mi (1,777.40 km) |
| Rio Maior to Ohrdruf | 1,238.70 mi (1,993.49 km) |
| Rio Maior to Ohringen | 1,133.63 mi (1,824.41 km) |
| Rio Maior to Olbernhau | 1,331.80 mi (2,143.33 km) |
| Rio Maior to Olching | 1,176.21 mi (1,892.93 km) |
| Rio Maior to Oldenburg | 1,251.19 mi (2,013.60 km) |
| Rio Maior to Oldenburg in Holstein | 1,385.85 mi (2,230.31 km) |
| Rio Maior to Olfen | 1,159.20 mi (1,865.55 km) |
| Rio Maior to Olpe | 1,143.16 mi (1,839.74 km) |
| Rio Maior to Olsberg | 1,179.52 mi (1,898.26 km) |
| Rio Maior to Oranienburg | 1,400.41 mi (2,253.74 km) |
| Rio Maior to Ortenberg | 1,159.26 mi (1,865.65 km) |
