| Mercer Island to Orbetello | 5,599.78 mi (9,011.98 km) |
| Mercer Island to Oria | 5,873.28 mi (9,452.14 km) |
| Mercer Island to Oristano | 5,681.86 mi (9,144.08 km) |
| Mercer Island to Orta Nova | 5,777.18 mi (9,297.47 km) |
| Mercer Island to Orte | 5,627.89 mi (9,057.21 km) |
| Mercer Island to Ortona | 5,683.56 mi (9,146.81 km) |
| Mercer Island to Orvieto | 5,605.49 mi (9,021.16 km) |
| Mercer Island to Orzinuovi | 5,391.00 mi (8,675.97 km) |
| Mercer Island to Osimo | 5,592.64 mi (9,000.48 km) |
| Mercer Island to Ospitaletto | 5,385.24 mi (8,666.70 km) |
| Mercer Island to Ostuni | 5,857.64 mi (9,426.96 km) |
| Mercer Island to Ottaviano | 5,777.10 mi (9,297.34 km) |
| Mercer Island to Ovada | 5,403.57 mi (8,696.21 km) |
| Mercer Island to Ozieri | 5,652.77 mi (9,097.26 km) |
| Mercer Island to Paceco | 5,902.94 mi (9,499.87 km) |
