If you really care about keeping our planet's surfaces green rather than paved with asphalt jungle (and you can afford it), then building down instead of up is the best way to do it.

Two British companies, NC Homes and Huntsmere, created a functional dwelling, built completely underground, under the Earth's surface in Bowdon, Manchester. This home is just as modern (perhaps even more) and luxurious as any other traditional house. They called it Perdu.

The circular three-bedroom home comes with a full kitchen, living area, and workout space. Above it there is a lovely decorative garden. According to its architects, the house has a more stable environment, the temperature remains constant and the house is very quiet and peaceful - all because it was built underground.

Perdu leaves a lot of green space available for planting on the roof. Since the house is circular, plenty of natural daylight enters through its central core, right down to the swimming pool, which is three floors down.

Estimated price? £2.5 million.