| Boppard to Smolyan | 1,012.74 mi (1,629.84 km) |
| Boppard to Sofia | 909.12 mi (1,463.08 km) |
| Boppard to Sopot | 966.97 mi (1,556.19 km) |
| Boppard to Sozopol | 1,095.94 mi (1,763.75 km) |
| Boppard to Sredets | 1,078.25 mi (1,735.28 km) |
| Boppard to Stamboliyski | 981.23 mi (1,579.13 km) |
| Boppard to Stara Zagora | 1,012.14 mi (1,628.88 km) |
| Boppard to Svilengrad | 1,063.05 mi (1,710.81 km) |
| Boppard to Svishtov | 951.16 mi (1,530.75 km) |
| Boppard to Targovishte | 1,016.40 mi (1,635.74 km) |
| Boppard to Teteven | 936.32 mi (1,506.87 km) |
| Boppard to Troyan | 955.65 mi (1,537.96 km) |
| Boppard to Tryavna | 987.76 mi (1,589.65 km) |
| Boppard to Tutrakan | 987.17 mi (1,588.70 km) |
| Boppard to Varna | 1,073.08 mi (1,726.95 km) |
