| Gretna to Oerlinghausen | 4,963.10 mi (7,987.34 km) |
| Gretna to Oestrich-Winkel | 4,995.83 mi (8,040.01 km) |
| Gretna to Offenburg | 5,039.43 mi (8,110.18 km) |
| Gretna to Oftersheim | 5,038.39 mi (8,108.50 km) |
| Gretna to Ohrdruf | 5,077.90 mi (8,172.09 km) |
| Gretna to Ohringen | 5,080.55 mi (8,176.35 km) |
| Gretna to Olbernhau | 5,183.30 mi (8,341.71 km) |
| Gretna to Olching | 5,186.00 mi (8,346.07 km) |
| Gretna to Oldenburg | 4,911.18 mi (7,903.78 km) |
| Gretna to Oldenburg in Holstein | 4,974.84 mi (8,006.23 km) |
| Gretna to Olfen | 4,920.89 mi (7,919.40 km) |
| Gretna to Olpe | 4,958.95 mi (7,980.66 km) |
| Gretna to Olsberg | 4,974.45 mi (8,005.61 km) |
| Gretna to Oranienburg | 5,109.94 mi (8,223.66 km) |
| Gretna to Ortenberg | 5,026.99 mi (8,090.17 km) |
