Which of these is a natural area of roughly 16 square km (6.2 squ miles), which is 5 km (3.1 miles) west of Tuktoyaktuk, Canada, in a coastal region of the Arctic Ocean, which contains approximately 1,350 Arctic ice dome hills?
Opened in 1890, with 6 stations over 3.2 miles (5.1 km) and running in a pair of tunnels between the City of London and Stockwell passing under the River Thames, what was the first deep-level underground "tube" railway in the world, and the first major railway to use electric traction?
What natural ice 1,212.5 metre (3,978 ft) long racing sled run in the Swiss town of St. Moritz, based on a river, was built in 1884?
What is the name of the 3.5-mile-long (5,600 m), 5.5 km wide semi-circular scalloped precipice in the Grand Coulee in Washington, USA?
What is the name for the highly viscous layer of the earth that is about 2,890 km (1,800 miles) thick and makes up about 84 percent of Earth's volume?