| Boulder City to Smolyan | 6,508.90 mi (10,475.07 km) |
| Boulder City to Sofia | 6,406.20 mi (10,309.79 km) |
| Boulder City to Sopot | 6,447.57 mi (10,376.36 km) |
| Boulder City to Sozopol | 6,537.99 mi (10,521.87 km) |
| Boulder City to Sredets | 6,529.32 mi (10,507.92 km) |
| Boulder City to Stamboliyski | 6,472.09 mi (10,415.82 km) |
| Boulder City to Stara Zagora | 6,484.21 mi (10,435.33 km) |
| Boulder City to Svilengrad | 6,538.21 mi (10,522.23 km) |
| Boulder City to Svishtov | 6,406.40 mi (10,310.10 km) |
| Boulder City to Targovishte | 6,459.84 mi (10,396.12 km) |
| Boulder City to Teteven | 6,418.98 mi (10,330.35 km) |
| Boulder City to Troyan | 6,432.97 mi (10,352.86 km) |
| Boulder City to Tryavna | 6,454.62 mi (10,387.71 km) |
| Boulder City to Tutrakan | 6,412.98 mi (10,320.70 km) |
| Boulder City to Varna | 6,495.28 mi (10,453.14 km) |
