| Watford to Oberkirch | 432.94 mi (696.75 km) |
| Watford to Obernburg am Main | 435.03 mi (700.11 km) |
| Watford to Obernkirchen | 406.94 mi (654.91 km) |
| Watford to Oberschleissheim | 580.62 mi (934.42 km) |
| Watford to Oberstdorf | 560.59 mi (902.19 km) |
| Watford to Obertraubling | 583.75 mi (939.46 km) |
| Watford to Obertshausen | 416.87 mi (670.88 km) |
| Watford to Oberursel | 403.12 mi (648.76 km) |
| Watford to Ochsenfurt | 478.31 mi (769.77 km) |
| Watford to Ochsenhausen | 522.32 mi (840.60 km) |
| Watford to Ochtrup | 325.27 mi (523.48 km) |
| Watford to Odenthal | 326.91 mi (526.11 km) |
| Watford to Oelde | 365.59 mi (588.36 km) |
| Watford to Oelsnitz | 551.77 mi (887.98 km) |
| Watford to Oer-Erkenschwick | 327.67 mi (527.33 km) |
