| Birsfelden to Smolyan | 933.60 mi (1,502.49 km) |
| Birsfelden to Sofia | 833.93 mi (1,342.08 km) |
| Birsfelden to Sopot | 898.95 mi (1,446.72 km) |
| Birsfelden to Sozopol | 1,039.74 mi (1,673.30 km) |
| Birsfelden to Sredets | 1,019.12 mi (1,640.11 km) |
| Birsfelden to Stamboliyski | 906.64 mi (1,459.10 km) |
| Birsfelden to Stara Zagora | 946.42 mi (1,523.12 km) |
| Birsfelden to Svilengrad | 993.45 mi (1,598.80 km) |
| Birsfelden to Svishtov | 896.96 mi (1,443.52 km) |
| Birsfelden to Targovishte | 963.79 mi (1,551.06 km) |
| Birsfelden to Teteven | 868.69 mi (1,398.02 km) |
| Birsfelden to Troyan | 889.99 mi (1,432.30 km) |
| Birsfelden to Tryavna | 925.88 mi (1,490.06 km) |
| Birsfelden to Tutrakan | 943.69 mi (1,518.72 km) |
| Birsfelden to Varna | 1,025.92 mi (1,651.06 km) |
