Work has involved the cutting of several hard rock tunnels beneath the sea cliffs.

Finally, here it was, a place to hide from the wind: a rock tunnel into the mountain.

The swan man disappeared into the rock tunnel.

The coal was reached through an 800-foot rock tunnel.

He felt cooler air around him, which suggested they had reached the rock tunnel on the far side of the room.

He descended a suddenly steeper slope to what looked like a natural doorway in the rock tunnel.

There's the first of the real rock tunnels coming up in a moment.

I can't begin to explain how this solid rock tunnel was bored.

The rock tunnel, completed in January 1861, is 141 feet long, 17 feet, 10 inches high and 40 feet wide.

At the same time, the rock tunnel can offer a kind of peace and solitude unique in the wide, uncovered Central Park.