| Niagara Falls to Opwijk | 3,743.94 mi (6,025.30 km) |
| Niagara Falls to Ostend | 3,686.83 mi (5,933.37 km) |
| Niagara Falls to Oud-Heverlee | 3,766.90 mi (6,062.24 km) |
| Niagara Falls to Oud-Turnhout | 3,764.05 mi (6,057.65 km) |
| Niagara Falls to Oudenaarde | 3,724.79 mi (5,994.47 km) |
| Niagara Falls to Oudenburg | 3,691.24 mi (5,940.48 km) |
| Niagara Falls to Oupeye | 3,808.78 mi (6,129.64 km) |
| Niagara Falls to Overijse | 3,763.28 mi (6,056.41 km) |
| Niagara Falls to Overpelt | 3,783.88 mi (6,089.57 km) |
| Niagara Falls to Paal | 3,780.06 mi (6,083.42 km) |
| Niagara Falls to Peer | 3,787.95 mi (6,096.12 km) |
| Niagara Falls to Pepinster | 3,820.06 mi (6,147.80 km) |
| Niagara Falls to Peruwelz | 3,734.39 mi (6,009.92 km) |
| Niagara Falls to Perwez | 3,779.26 mi (6,082.12 km) |
| Niagara Falls to Philippeville | 3,782.29 mi (6,087.01 km) |
