Family builds twin underground homes in ancient mountain farm

René Douma and his mom Marianne began building houses into the hillside on the family farm without any experience in underground construction. Relying on books and online forums, they excavated a knoll behind their farmhouse and used 45 acacia trees from the property to shore up the walls and roof. After a waterproofing layer of asphalt fabric, they covered the homes with dirt and waited for the native grasses to grow back. Today, the twin homes are invisible from three sides; only the glass facade is visible from down the hill. Everything follows the slope of the land and shape of the wood beams so nothing is linear. The windows and curtains were handmade to fit the site. Even the beds were built using acacia branches. After completion, Marianne noticed one winter day that the sun had heated the south-facing space to 27°C (81°F) and decided to move from the drafty farmhouse to the 30m2 (323 sq ft) burrow for the winter. Her farmer neighbors started calling her the marmot, but she loved th