Introduction to the Old Plaza of Havana: The Old Plaza of Havana was built in the 16th century and was once an open-air market. There is the Camara Oscura (dark room observation deck) in the northeast corner of the old square. This observation deck was built in 2001. It was first designed by Leonardo da Vinci and donated by Spanish Congressman Cadiz. Light is reflected through a 180-meter-diameter mirror onto a recessed screen, allowing views within a radius of 5 kilometers. A unique view. There are currently 54 such darkrooms in the world, in countries such as Spain, the United Kingdom, and the United States.