| Guadarrama to Orbetello | 799.36 mi (1,286.44 km) |
| Guadarrama to Oria | 1,136.94 mi (1,829.73 km) |
| Guadarrama to Oristano | 669.82 mi (1,077.97 km) |
| Guadarrama to Orta Nova | 1,031.22 mi (1,659.60 km) |
| Guadarrama to Orte | 859.18 mi (1,382.71 km) |
| Guadarrama to Ortona | 961.65 mi (1,547.63 km) |
| Guadarrama to Orvieto | 846.24 mi (1,361.88 km) |
| Guadarrama to Orzinuovi | 778.43 mi (1,252.76 km) |
| Guadarrama to Osimo | 919.98 mi (1,480.57 km) |
| Guadarrama to Ospitaletto | 788.48 mi (1,268.94 km) |
| Guadarrama to Ostuni | 1,132.29 mi (1,822.24 km) |
| Guadarrama to Ottaviano | 969.90 mi (1,560.91 km) |
| Guadarrama to Ovada | 701.78 mi (1,129.40 km) |
| Guadarrama to Ozieri | 685.92 mi (1,103.88 km) |
| Guadarrama to Paceco | 907.01 mi (1,459.69 km) |
