Seoul’s new City Hall boasts a sprawling indoor green wall that’s so big it set a Guinness World Record as the world’s largest vertical garden in 2013. Designed by iArc Architects, the seven-story-high vertical garden was created to complement the new City Hall’s environmentally friendly features, including its numerous renewable energy sources from solar power to geothermal energy. Approximately 65,000 plants from 14 different species grow in the garden, which spans an area greater than 17,000 square feet.