| Boulder to Oberkirch | 5,090.58 mi (8,192.50 km) |
| Boulder to Obernburg am Main | 5,063.82 mi (8,149.43 km) |
| Boulder to Obernkirchen | 4,948.77 mi (7,964.27 km) |
| Boulder to Oberschleissheim | 5,219.14 mi (8,399.39 km) |
| Boulder to Oberstdorf | 5,217.65 mi (8,397.00 km) |
| Boulder to Obertraubling | 5,203.34 mi (8,373.96 km) |
| Boulder to Obertshausen | 5,043.12 mi (8,116.11 km) |
| Boulder to Oberursel | 5,028.37 mi (8,092.39 km) |
| Boulder to Ochsenfurt | 5,102.80 mi (8,212.16 km) |
| Boulder to Ochsenhausen | 5,174.67 mi (8,327.83 km) |
| Boulder to Ochtrup | 4,891.04 mi (7,871.37 km) |
| Boulder to Odenthal | 4,942.44 mi (7,954.08 km) |
| Boulder to Oelde | 4,938.61 mi (7,947.92 km) |
| Boulder to Oelsnitz | 5,132.18 mi (8,259.44 km) |
| Boulder to Oer-Erkenschwick | 4,918.79 mi (7,916.03 km) |
