Although the highest mountain peaks have been climbed and the densest forests have been visited, there are still about 140,000,000 square miles of unexplored area on earth. Those miles are found on the ocean floor, with its winding valleys, towering mountains, steep canyons, and vast plains.
On land, there are still some remote areas that can be reached only on foot. Some of these as yet unexplored places are in the mountains of New Guinea and in the jungles of Africa and the Amazon.
Then, too, there are the colder regions still to be visited and explored. However, these regions, the Greenland icecap, northwest Siberia, and Antarctica, can only be reached by dog teams.