| Fort Collins to Oberkirch | 5,056.42 mi (8,137.52 km) |
| Fort Collins to Obernburg am Main | 5,029.27 mi (8,093.83 km) |
| Fort Collins to Obernkirchen | 4,913.77 mi (7,907.95 km) |
| Fort Collins to Oberschleissheim | 5,184.59 mi (8,343.80 km) |
| Fort Collins to Oberstdorf | 5,183.43 mi (8,341.93 km) |
| Fort Collins to Obertraubling | 5,168.59 mi (8,318.04 km) |
| Fort Collins to Obertshausen | 5,008.56 mi (8,060.49 km) |
| Fort Collins to Oberursel | 4,993.82 mi (8,036.77 km) |
| Fort Collins to Ochsenfurt | 5,068.17 mi (8,156.44 km) |
| Fort Collins to Ochsenhausen | 5,140.36 mi (8,272.62 km) |
| Fort Collins to Ochtrup | 4,856.25 mi (7,815.38 km) |
| Fort Collins to Odenthal | 4,907.88 mi (7,898.47 km) |
| Fort Collins to Oelde | 4,903.79 mi (7,891.88 km) |
| Fort Collins to Oelsnitz | 5,097.18 mi (8,203.12 km) |
| Fort Collins to Oer-Erkenschwick | 4,884.10 mi (7,860.20 km) |
