Atop Nymph’s Hill, a quick climb from the Plaka, is the National Observatory of Athens, a research institute and true observatory. Visitors by day get a lovely view of the city from the tree-lined grounds which surround beautiful mid-19th-century neoclassical buildings designed by Theophil Hansen; and visitors by night get a chance to view celestial bodies through a 170-year-old telescope. In 2017, the observatory was the site of an extensive installation by Argentinean artist Adrián Villar Rojas.