| Watford to Hoyo de Manzanares | 779.37 mi (1,254.28 km) |
| Watford to Huelva | 1,045.42 mi (1,682.44 km) |
| Watford to Huercal de Almeria | 1,025.49 mi (1,650.36 km) |
| Watford to Huercal-Overa | 988.93 mi (1,591.52 km) |
| Watford to Huesca | 657.89 mi (1,058.77 km) |
| Watford to Huetor Vega | 1,014.10 mi (1,632.03 km) |
| Watford to Huetor-Tajar | 1,014.89 mi (1,633.30 km) |
| Watford to Humanes de Madrid | 804.57 mi (1,294.83 km) |
| Watford to Ibi | 900.18 mi (1,448.69 km) |
| Watford to Ibiza | 885.07 mi (1,424.38 km) |
| Watford to Icod de los Vinos | 1,817.44 mi (2,924.88 km) |
| Watford to Igualada | 702.49 mi (1,130.55 km) |
| Watford to Illescas | 813.94 mi (1,309.91 km) |
| Watford to Inca | 839.98 mi (1,351.81 km) |
| Watford to Ingenio | 1,815.63 mi (2,921.97 km) |
