| Romeoville to Orbetello | 4,764.55 mi (7,667.81 km) |
| Romeoville to Oria | 5,105.87 mi (8,217.11 km) |
| Romeoville to Oristano | 4,763.12 mi (7,665.50 km) |
| Romeoville to Orta Nova | 4,992.46 mi (8,034.59 km) |
| Romeoville to Orte | 4,810.76 mi (7,742.17 km) |
| Romeoville to Ortona | 4,895.51 mi (7,878.56 km) |
| Romeoville to Orvieto | 4,788.70 mi (7,706.68 km) |
| Romeoville to Orzinuovi | 4,590.64 mi (7,387.93 km) |
| Romeoville to Osimo | 4,810.16 mi (7,741.21 km) |
| Romeoville to Ospitaletto | 4,589.79 mi (7,386.55 km) |
| Romeoville to Ostuni | 5,093.23 mi (8,196.77 km) |
| Romeoville to Ottaviano | 4,964.71 mi (7,989.93 km) |
| Romeoville to Ovada | 4,570.63 mi (7,355.72 km) |
| Romeoville to Ozieri | 4,751.97 mi (7,647.55 km) |
| Romeoville to Paceco | 5,012.25 mi (8,066.44 km) |
