| Mason City to Nuth | 4,333.94 mi (6,974.81 km) |
| Mason City to Oegstgeest | 4,233.79 mi (6,813.63 km) |
| Mason City to Oirschot | 4,289.97 mi (6,904.03 km) |
| Mason City to Oisterwijk | 4,283.14 mi (6,893.04 km) |
| Mason City to Oldebroek | 4,272.96 mi (6,876.66 km) |
| Mason City to Oldenzaal | 4,313.77 mi (6,942.34 km) |
| Mason City to Ommen | 4,288.03 mi (6,900.91 km) |
| Mason City to Oosterend | 4,256.64 mi (6,850.40 km) |
| Mason City to Oosterhout | 4,268.71 mi (6,869.83 km) |
| Mason City to Oosterwolde | 4,264.82 mi (6,863.57 km) |
| Mason City to Oostzaan | 4,238.50 mi (6,821.21 km) |
| Mason City to Opmeer | 4,230.36 mi (6,808.10 km) |
| Mason City to Oss | 4,286.92 mi (6,899.12 km) |
| Mason City to Oud-Beijerland | 4,245.81 mi (6,832.97 km) |
| Mason City to Oudenbosch | 4,259.12 mi (6,854.39 km) |
