| Greenbelt to Oerlinghausen | 3,994.20 mi (6,428.05 km) |
| Greenbelt to Oestrich-Winkel | 4,023.13 mi (6,474.60 km) |
| Greenbelt to Offenburg | 4,064.88 mi (6,541.79 km) |
| Greenbelt to Oftersheim | 4,065.08 mi (6,542.12 km) |
| Greenbelt to Ohrdruf | 4,107.97 mi (6,611.14 km) |
| Greenbelt to Ohringen | 4,107.40 mi (6,610.22 km) |
| Greenbelt to Olbernhau | 4,214.71 mi (6,782.92 km) |
| Greenbelt to Olching | 4,212.38 mi (6,779.17 km) |
| Greenbelt to Oldenburg | 3,944.66 mi (6,348.31 km) |
| Greenbelt to Oldenburg in Holstein | 4,013.37 mi (6,458.90 km) |
| Greenbelt to Olfen | 3,950.77 mi (6,358.15 km) |
| Greenbelt to Olpe | 3,987.78 mi (6,417.72 km) |
| Greenbelt to Olsberg | 4,004.23 mi (6,444.18 km) |
| Greenbelt to Oranienburg | 4,146.10 mi (6,672.51 km) |
| Greenbelt to Ortenberg | 4,055.33 mi (6,526.42 km) |
