| Watford to Opole | 795.03 mi (1,279.48 km) |
| Watford to Orzesze | 838.23 mi (1,349.01 km) |
| Watford to Osowa | 804.14 mi (1,294.14 km) |
| Watford to Ostroda | 861.55 mi (1,386.52 km) |
| Watford to Ostroleka | 928.11 mi (1,493.66 km) |
| Watford to Ostrow Mazowiecka | 943.08 mi (1,517.74 km) |
| Watford to Ostrow Wielkopolski | 778.68 mi (1,253.17 km) |
| Watford to Ostrowiec Swietokrzyski | 939.51 mi (1,512.00 km) |
| Watford to Ostrzeszow | 785.84 mi (1,264.69 km) |
| Watford to Oswiecim | 860.41 mi (1,384.69 km) |
| Watford to Otwock | 920.94 mi (1,482.11 km) |
| Watford to Ozarow Mazowiecki | 900.53 mi (1,449.26 km) |
| Watford to Ozimek | 806.92 mi (1,298.62 km) |
| Watford to Ozorkow | 838.35 mi (1,349.19 km) |
| Watford to Pabianice | 845.28 mi (1,360.34 km) |
