The World's Most Extraordinary Homes

In episode one, their journey starts in the Santa Monica mountains in California, where one homeowner built her dream home from the most unthinkable re-used building material - the wings and tail fins of a disused Boeing 747, which had to be delivered onto the mountain site by helicopter.

Their next stop takes them to the desert Tuscon Mountain Range of Arizona, where Caroline and Piers spend the day and stay overnight in a stunning modern house which is heavily influenced by ancient building methods. The home has an innovative take on traditional rammed earth houses, a centuries-old technique that absorbs the heat during the day and releases it at night, reducing the need for air-conditioning and heating.

Next, Caroline and Piers go to the other side of the world to New Zealand's South Island. Designed to fit within strict planning regulations, the house was inspired by the surrounding trees and mountains and is camouflaged using wooden cedar cladding to cloak the building, and with fireplaces cast in concrete.

The last stop takes them to the Swiss Alps, to a unique alpine chalet. Arriving by cable car, Piers and Caroline discover it's hexagonal shape gives it stability in the freezing winter winds, while the steel chimney core that anchors the house to the mountain also distributes heat around the house. As the mists clear, an incredible panoramic view of the Alps is revealed.