| Upper Grand Lagoon to Orbetello | 5,169.41 mi (8,319.37 km) |
| Upper Grand Lagoon to Oria | 5,524.77 mi (8,891.25 km) |
| Upper Grand Lagoon to Oristano | 5,126.63 mi (8,250.51 km) |
| Upper Grand Lagoon to Orta Nova | 5,409.18 mi (8,705.24 km) |
| Upper Grand Lagoon to Orte | 5,221.78 mi (8,403.65 km) |
| Upper Grand Lagoon to Ortona | 5,315.71 mi (8,554.80 km) |
| Upper Grand Lagoon to Orvieto | 5,201.06 mi (8,370.30 km) |
| Upper Grand Lagoon to Orzinuovi | 5,021.27 mi (8,080.95 km) |
| Upper Grand Lagoon to Osimo | 5,237.40 mi (8,428.78 km) |
| Upper Grand Lagoon to Ospitaletto | 5,022.72 mi (8,083.29 km) |
| Upper Grand Lagoon to Ostuni | 5,514.15 mi (8,874.17 km) |
| Upper Grand Lagoon to Ottaviano | 5,369.90 mi (8,642.01 km) |
| Upper Grand Lagoon to Ovada | 4,987.03 mi (8,025.86 km) |
| Upper Grand Lagoon to Ozieri | 5,125.22 mi (8,248.24 km) |
| Upper Grand Lagoon to Paceco | 5,376.66 mi (8,652.90 km) |
