| Catonsville to Oerlinghausen | 3,975.73 mi (6,398.32 km) |
| Catonsville to Oestrich-Winkel | 4,005.01 mi (6,445.43 km) |
| Catonsville to Offenburg | 4,047.02 mi (6,513.05 km) |
| Catonsville to Oftersheim | 4,047.03 mi (6,513.07 km) |
| Catonsville to Ohrdruf | 4,089.58 mi (6,581.55 km) |
| Catonsville to Ohringen | 4,089.33 mi (6,581.14 km) |
| Catonsville to Olbernhau | 4,196.23 mi (6,753.17 km) |
| Catonsville to Olching | 4,194.38 mi (6,750.20 km) |
| Catonsville to Oldenburg | 3,926.03 mi (6,318.33 km) |
| Catonsville to Oldenburg in Holstein | 3,994.48 mi (6,428.49 km) |
| Catonsville to Olfen | 3,932.39 mi (6,328.57 km) |
| Catonsville to Olpe | 3,969.50 mi (6,388.29 km) |
| Catonsville to Olsberg | 3,985.86 mi (6,414.62 km) |
| Catonsville to Oranienburg | 4,127.33 mi (6,642.30 km) |
| Catonsville to Ortenberg | 4,037.09 mi (6,497.07 km) |
