| Watford to Nasaud | 1,147.67 mi (1,847.00 km) |
| Watford to Navodari | 1,422.47 mi (2,289.25 km) |
| Watford to Negresti-Oas | 1,089.49 mi (1,753.37 km) |
| Watford to Nehoiu | 1,288.86 mi (2,074.22 km) |
| Watford to Ocna Mures | 1,151.34 mi (1,852.90 km) |
| Watford to Odobesti | 1,307.45 mi (2,104.13 km) |
| Watford to Odorheiu Secuiesc | 1,214.91 mi (1,955.21 km) |
| Watford to Oltenita | 1,347.76 mi (2,169.01 km) |
| Watford to Onesti | 1,279.10 mi (2,058.51 km) |
| Watford to Oradea | 1,048.14 mi (1,686.81 km) |
| Watford to Orastie | 1,141.11 mi (1,836.44 km) |
| Watford to Oravita | 1,106.53 mi (1,780.78 km) |
| Watford to Orsova | 1,147.57 mi (1,846.83 km) |
| Watford to Otelu Rosu | 1,117.01 mi (1,797.66 km) |
| Watford to Otopeni | 1,307.06 mi (2,103.50 km) |
