The "double loop" tunnel. Originally the train track ascended a 4.5% grade to get to Banff, which was over twice what was allowed. After numerous wrecks, an idea was taken from Switzerland and tunnel loops were cut through the mountains. Now, the train ascends the valley and enters the opposite mountain (center) and emerges above it (upper left) . Then, it crosses over to the near side (locomotives below, going right-to-left) and makes a loop inside this mountain, emerging above this location heading to the right, uphill again. The last car had just disappeared into the entrance to the first tunnel as the locomotives came into sight below.