Some claim that thousands of people live underground in Europe and America. Notable European examples are the "Earth Houses" of Swiss architect Peter Vetsch. There are about 50 such earth shelters in Switzerland, including a residential estate of nine earth shelters (Lättenstrasse in Dietikon). Possibly the most well known examples of modern earth sheltering in the English-speaking world are Earthships, the brand of passive solar earth shelters sold by Earthship Biotecture. Earthships are concentrated in New Mexico, USA, but are found less commonly throughout the world. In other areas such as the UK earth sheltering is more uncommon.