Wikipedia explains: "The Ciudad Mitad del Mundo (Middle of the World City) is a tract of land owned by the prefecture of the province of Pichincha, Ecuador. It is located at San Antonio parish of the canton of Quito, 26 km north of the center of Quito. The grounds contain the Monument to the Equator, which highlights the exact location of the Equator (from which the country takes its name) and commemorates the eighteenth century Franco-Spanish Geodesic Mission which fixed its approximate location; they also contain the Museo Etnografico Mitad del Mundo, a museum about the indigenous ethnography of Ecuador.
"The 30-meter-tall monument was constructed between 1979 and 1982 by Pichincha's Province Council to replace an older, smaller monument built by Government of Ecuador under the direction of the geographer Luis Tufino in 1936. It is made of iron and concrete and covered with cut and polished andesite stone. The monument was built to commemorate the first Geodesic Mission of the French Academy of Sciences, led by Louis Godin, Pierre Bouguer and Charles Marie de La Condamine, who, in the year 1736, conducted experiments to test the flattening at the poles of the characteristic shape of the Earth, by comparing the distance between a degree meridian in the equatorial zone to another level measured in Sweden. The older monument was moved 7 km to a small town near there called Calacali."