The Circle Line and the three other lines it shares tracks with date from mid-Victorian times, and were originally worked by steam trains, which of course needed ventilation to allow the steam to escape.
The Circle Line and the three other lines it shares tracks with date from mid-Victorian times, and were originally worked by steam trains, which of course needed ventilation to allow the steam to escape.
环线地铁和轨道与之有重叠的其他三条地铁线可追溯到维多利亚时代中期，而且最初运行的是蒸气火车，当然，需要通风设施使蒸气逸出。