| Mountain Ash to Oerlinghausen | 514.21 mi (827.54 km) |
| Mountain Ash to Oestrich-Winkel | 509.32 mi (819.67 km) |
| Mountain Ash to Offenburg | 547.86 mi (881.69 km) |
| Mountain Ash to Oftersheim | 548.50 mi (882.72 km) |
| Mountain Ash to Ohrdruf | 612.11 mi (985.10 km) |
| Mountain Ash to Ohringen | 591.19 mi (951.43 km) |
| Mountain Ash to Olbernhau | 725.74 mi (1,167.97 km) |
| Mountain Ash to Olching | 694.87 mi (1,118.28 km) |
| Mountain Ash to Oldenburg | 498.34 mi (802.00 km) |
| Mountain Ash to Oldenburg in Holstein | 618.92 mi (996.05 km) |
| Mountain Ash to Olfen | 460.48 mi (741.07 km) |
| Mountain Ash to Olpe | 485.55 mi (781.42 km) |
| Mountain Ash to Olsberg | 510.00 mi (820.77 km) |
| Mountain Ash to Oranienburg | 705.67 mi (1,135.67 km) |
| Mountain Ash to Ortenberg | 547.46 mi (881.06 km) |
