These are among the best locations for astronomical observations in the southern hemisphere. An ESO project is the Extremely Large Telescope (ELT), a 40-metre-class telescope based on a five-mirror design and the formerly planned Overwhelmingly Large Telescope. The ELT will be the largest visible and near-infrared telescope in the world. ESO began its design in early 2006, and aimed to begin construction in 2012. Construction work at the ELT site started in June 2014. As decided by the ESO council on 26 April 2010, a fourth site (Cerro Armazones) is to be home to ELT.