Situated in the US city of Silver Spring, Maryland, the 210,000 square-foot, ellipse-shaped Unisphere is the world’s largest commercial net-zero building. Completed in 2018, it houses biotech corporation United Therapeutics’ clinical operations and virtual drug development lab. The building has no operational carbon footprint because the amount of electrical and thermal energy used is renewably generated on-site. Unisphere is heated and cooled with water pulled from 52 geo-exchange wells drilled 500ft into the earth below. The building “breathes naturally, as weather changes and seasons evolve”: artificial lighting dims automatically and windows change their tint based on sunlight and cloud cover.