From the World Heritage inscription:
Quito, the capital of Ecuador, was founded in the 16th century on the ruins of an Inca city and stands at an altitude of 2,850 m. Despite the 1917 earthquake, the city has the best-preserved, least altered historic centre in Latin America. The monasteries of San Francisco and Santo Domingo, and the Church and Jesuit College of La Compañía, with their rich interiors, are pure examples of the ‘Baroque school of Quito’, which is a fusion of Spanish, Italian, Moorish, Flemish and indigenous art.
Quito was the first cultural World Heritage site and the second overall after the Galapagos Islands. Quito is considered to be one of the best preserved Spanish colonial cities in Latin American and the best capital city. The highlight of the old city to me was the cathedral. If you should find yourself at the Quito Cathedral, check out the gargoyles on the outside. They are all animals you will find in Ecuador and the Galapagos Islands, including marine iguanas and tortoises.
View my complete list of UNESCO World Heritage sites.