Batasia Loop was commissioned in 1919 because it was an engineering requirement for the toy train to be able to handle a steep gradient. Just after Ghoom (which is the highest railway station) there is a sharp fall as the toy train moves towards Darjeeling. There was no way the toy train could negotiate such a drastic fall of about 140ft unless there was a way to somehow reduce the gradient of the slope.
Batasia Loop was created by the British to counter such sharp descent. You won't even realize how the toy train actually descends by about 140ft as it completes the loop through a large circular area and on a gentle slope and then crosses its own track near the beginning of the loop through a tunnel below. It is considered as one of the greatest engineering feats.
