| Boulder to Cadiz | 5,065.68 mi (8,152.43 km) |
| Boulder to Calafell | 5,189.95 mi (8,352.41 km) |
| Boulder to Calahorra | 5,001.12 mi (8,048.52 km) |
| Boulder to Calasparra | 5,189.37 mi (8,351.48 km) |
| Boulder to Calatayud | 5,055.60 mi (8,136.20 km) |
| Boulder to Caldas de Montbuy | 5,193.90 mi (8,358.77 km) |
| Boulder to Caldas de Reyes | 4,716.24 mi (7,590.05 km) |
| Boulder to Calella | 5,213.97 mi (8,391.07 km) |
| Boulder to Callosa de Segura | 5,228.37 mi (8,414.24 km) |
| Boulder to Calpe | 5,243.27 mi (8,438.22 km) |
| Boulder to Calvia | 5,301.31 mi (8,531.63 km) |
| Boulder to Camas | 5,040.49 mi (8,111.89 km) |
| Boulder to Cambados | 4,713.57 mi (7,585.75 km) |
| Boulder to Cambre | 4,701.94 mi (7,567.04 km) |
| Boulder to Cambrils | 5,175.66 mi (8,329.42 km) |
