| Round Rock to Orbetello | 5,673.95 mi (9,131.34 km) |
| Round Rock to Oria | 6,020.43 mi (9,688.94 km) |
| Round Rock to Oristano | 5,658.78 mi (9,106.92 km) |
| Round Rock to Orta Nova | 5,906.06 mi (9,504.88 km) |
| Round Rock to Orte | 5,722.14 mi (9,208.89 km) |
| Round Rock to Ortona | 5,809.75 mi (9,349.89 km) |
| Round Rock to Orvieto | 5,700.39 mi (9,173.89 km) |
| Round Rock to Orzinuovi | 5,506.69 mi (8,862.17 km) |
| Round Rock to Osimo | 5,726.02 mi (9,215.14 km) |
| Round Rock to Ospitaletto | 5,506.43 mi (8,861.75 km) |
| Round Rock to Ostuni | 6,008.29 mi (9,669.42 km) |
| Round Rock to Ottaviano | 5,874.91 mi (9,454.75 km) |
| Round Rock to Ovada | 5,482.72 mi (8,823.59 km) |
| Round Rock to Ozieri | 5,651.04 mi (9,094.47 km) |
| Round Rock to Paceco | 5,909.26 mi (9,510.03 km) |
