De Architectura is a set of 10 books written between 30 and 15 BC by Vitruvius on Roman architecture. They were dedicated to the emperor of the day, Emperor Caesar Augustus. It covers a variety of subjects, including the building materials used in construction, different types of building designs, aqueduct designs, and explanations of how to use and construct machines used in the construction process. It was rediscovered in the 15th century and became a prominent influence in Renaissance architecture, eventually leading to the reintroduction of the classical style into architecture of the day. The photo is by Mark Pellegrini (Own work) [CC BY-SA 2.5 (http://creativecommons.org/licenses/by-sa/2.5)], via Wikimedia Commons. It is free to copy and distribute.