| Lake Monticello to Orbetello | 4,505.22 mi (7,250.45 km) |
| Lake Monticello to Oria | 4,858.42 mi (7,818.87 km) |
| Lake Monticello to Oristano | 4,472.92 mi (7,198.46 km) |
| Lake Monticello to Orta Nova | 4,742.99 mi (7,633.11 km) |
| Lake Monticello to Orte | 4,556.34 mi (7,332.72 km) |
| Lake Monticello to Ortona | 4,648.50 mi (7,481.04 km) |
| Lake Monticello to Orvieto | 4,535.26 mi (7,298.79 km) |
| Lake Monticello to Orzinuovi | 4,351.13 mi (7,002.46 km) |
| Lake Monticello to Osimo | 4,568.51 mi (7,352.31 km) |
| Lake Monticello to Ospitaletto | 4,352.14 mi (7,004.09 km) |
| Lake Monticello to Ostuni | 4,847.33 mi (7,801.02 km) |
| Lake Monticello to Ottaviano | 4,706.23 mi (7,573.94 km) |
| Lake Monticello to Ovada | 4,319.72 mi (6,951.92 km) |
| Lake Monticello to Ozieri | 4,468.82 mi (7,191.87 km) |
| Lake Monticello to Paceco | 4,723.60 mi (7,601.89 km) |
