| Piqua to Oerlinghausen | 4,218.52 mi (6,789.05 km) |
| Piqua to Oestrich-Winkel | 4,260.28 mi (6,856.25 km) |
| Piqua to Offenburg | 4,310.86 mi (6,937.66 km) |
| Piqua to Oftersheim | 4,304.71 mi (6,927.76 km) |
| Piqua to Ohrdruf | 4,335.05 mi (6,976.59 km) |
| Piqua to Ohringen | 4,346.19 mi (6,994.51 km) |
| Piqua to Olbernhau | 4,437.47 mi (7,141.42 km) |
| Piqua to Olching | 4,453.00 mi (7,166.40 km) |
| Piqua to Oldenburg | 4,162.63 mi (6,699.10 km) |
| Piqua to Oldenburg in Holstein | 4,219.40 mi (6,790.47 km) |
| Piqua to Olfen | 4,178.93 mi (6,725.34 km) |
| Piqua to Olpe | 4,219.30 mi (6,790.31 km) |
| Piqua to Olsberg | 4,232.56 mi (6,811.65 km) |
| Piqua to Oranienburg | 4,357.01 mi (7,011.93 km) |
| Piqua to Ortenberg | 4,288.40 mi (6,901.51 km) |
