Kicking Horse Pass spiral tunnels view, Canada

This pass in the Canadian Rockies at the Alberta–British Columbia border and the Banff–Yoho national parks boundary is the highest point on the Canadian Pacific Railway, at an elevation of 5,338 feet [1,627 metres]. The approach from the east is by way of the Bow Valley; from the west end, two circular tunnels were cut into the valley sides (completed in 1911) to reduce the gradient of the railway. It was explored in 1858 by James Hector of Captain John Palliser’s expedition. Hector was kicked by his horse while crossing the pass—hence its name.

The Trans-Canada Highway came through the pass in the 1960s.The tunnel under Cathedral mountain is 3,255 feet [992 metres] long with a turn of 291 degrees, and the one under Mount Ogden turns through 217 degrees over 2,992 feet [912 metres]. The ruling grade is 2.2%. The tunnels were completed in August 1909, and replaced the route up the "Big Hill", which had a 4.5% grade. There is/was a lookout just off the Trans-Canada Highway from which you could observe both portals of the tunnel. Passengers can ride this route, at least in the summer, on Great Canadian Railtours' Rocky Mountaineer train from Calgary to Vancouver.

When the tunnels had been bored, they were off on one tunnel by 18 inches when the two ends connected, and 6 inches on the other. (via Britannica Online)