| Greenbelt to Orbetello | 4,398.75 mi (7,079.11 km) |
| Greenbelt to Oria | 4,751.70 mi (7,647.12 km) |
| Greenbelt to Oristano | 4,367.63 mi (7,029.01 km) |
| Greenbelt to Orta Nova | 4,636.30 mi (7,461.40 km) |
| Greenbelt to Orte | 4,449.73 mi (7,161.16 km) |
| Greenbelt to Ortona | 4,541.72 mi (7,309.19 km) |
| Greenbelt to Orvieto | 4,428.62 mi (7,127.17 km) |
| Greenbelt to Orzinuovi | 4,244.09 mi (6,830.20 km) |
| Greenbelt to Osimo | 4,461.57 mi (7,180.20 km) |
| Greenbelt to Ospitaletto | 4,245.05 mi (6,831.76 km) |
| Greenbelt to Ostuni | 4,740.57 mi (7,629.20 km) |
| Greenbelt to Ottaviano | 4,599.79 mi (7,402.65 km) |
| Greenbelt to Ovada | 4,212.95 mi (6,780.09 km) |
| Greenbelt to Ozieri | 4,363.21 mi (7,021.91 km) |
| Greenbelt to Paceco | 4,618.34 mi (7,432.49 km) |
