| Boulder to Cocentaina | 5,218.85 mi (8,398.93 km) |
| Boulder to Coin | 5,127.53 mi (8,251.97 km) |
| Boulder to Colindres | 4,895.32 mi (7,878.26 km) |
| Boulder to Collado-Villalba | 4,989.37 mi (8,029.62 km) |
| Boulder to Colmenar Viejo | 4,998.30 mi (8,043.99 km) |
| Boulder to Colmenarejo | 4,992.10 mi (8,034.00 km) |
| Boulder to Conil de la Frontera | 5,086.47 mi (8,185.89 km) |
| Boulder to Consuegra | 5,056.11 mi (8,137.02 km) |
| Boulder to Corbera de Llobregat | 5,194.42 mi (8,359.61 km) |
| Boulder to Cordoba | 5,074.03 mi (8,165.86 km) |
| Boulder to Coria del Rio | 5,044.79 mi (8,118.80 km) |
| Boulder to Crevillente | 5,225.70 mi (8,409.96 km) |
| Boulder to Cuarte de Huerva | 5,074.21 mi (8,166.15 km) |
| Boulder to Cubellas | 5,193.63 mi (8,358.33 km) |
| Boulder to Cuellar | 4,944.32 mi (7,957.11 km) |
