Where did the children go the first afternoon in The Railway Children?

When their father's arrest forces the children to move with their mother to a new and poorer home, far from where they used to live, the children go down to see the railway the first afternoon they are there. They arrived the night before; the next morning and early afternoon, they helped their mother unpack and get the house settled. Finally, in the late afternoon, they are free to play.
They had glimpsed the railway from afar that morning when they had had a few minutes to explore, and that is what they all want to see again. They head for it:

The way to the railway was all down hill over smooth, short turf with here and there furze bushes and grey and yellow rocks sticking out like candied peel from the top of a cake.
The way ended in a steep run and a wooden fence—and there was the railway with the shining metals and the telegraph wires and posts and signals.

They climb a fence for a better view. The railway line, the tunnel, and the trains rushing past all exercise a hold on the children's imagination. They go to the railway station as often as they can, and it becomes central to the plot of the book.