The Illuminated Block (Spanish: Manzana de las Luces) is a historical landmark in the Monserrat neighbourhood of Buenos Aires, Argentina. The Society of Jesus arrived in the newly-founded village of Buenos Ayres in 1608, establishing their first mission on a 2 hectare (5 acre) lot which had earlier been aside by Spanish conquistador Juan de Garay for the future town square. The Jesuits' 1661 sale of the property (which would ultimately become the Plaza de Mayo) and a gift of an adjacent lot by Isabel de Carvajal allowed the order to build a new, largely self-reliant mission. Work began in 1686 on the Parish of St. Ignatius, a baroque structure completed in 1722, and the adjoining College of St. Ignatius was designed by local architect Juan Kraus and built between 1710 and 1729.
Becoming the only academy in colonial Buenos Aires to provide a classical education, and the property possessed the city's finest laboratories, museum and library. The center housed the Office of the Advocate General of the Missions (which oversaw the order's numerous, lucrative Indian Reductions), as well as a pharmacy (the city's first) opened and operated by an English Jesuit, Father Thomas Falkner. The center later had an anecdotal role in the Argentine War of Independence. The Regiment of Patricians was briefly headquartered in 1811 at the college, where the regiment staged a failed mutiny against their commander, General Manuel Belgrano.
A network of five underground tunnels intersecting under the former mission (believed to have been built to guarantee the flow of supplies in the event of a siege, and to facilitate smuggling in peacetime) helped safeguard ammunitions during much of the war. The provisional government organized from the May Revolution of 1810, the First Assembly, opened a public library in 1812, and following the War of Independence, Governor Martín Rodríguez inaugurated the University of Buenos Aires and the General Archive, in 1821. A few days later, the city's leading newspaper, El Argos, described the area as the "Illuminated Block" in a September 1, 1821, editorial.