| Rhondda to Smolyan | 1,491.13 mi (2,399.75 km) |
| Rhondda to Sofia | 1,388.84 mi (2,235.12 km) |
| Rhondda to Sopot | 1,449.69 mi (2,333.05 km) |
| Rhondda to Sozopol | 1,582.31 mi (2,546.49 km) |
| Rhondda to Sredets | 1,563.92 mi (2,516.89 km) |
| Rhondda to Stamboliyski | 1,461.51 mi (2,352.08 km) |
| Rhondda to Stara Zagora | 1,495.79 mi (2,407.23 km) |
| Rhondda to Svilengrad | 1,545.56 mi (2,487.34 km) |
| Rhondda to Svishtov | 1,437.56 mi (2,313.53 km) |
| Rhondda to Targovishte | 1,503.27 mi (2,419.28 km) |
| Rhondda to Teteven | 1,419.05 mi (2,283.74 km) |
| Rhondda to Troyan | 1,439.10 mi (2,316.01 km) |
| Rhondda to Tryavna | 1,472.46 mi (2,369.69 km) |
| Rhondda to Tutrakan | 1,475.18 mi (2,374.08 km) |
| Rhondda to Varna | 1,560.85 mi (2,511.94 km) |
