The document summarizes key Roman engineering structures - the Colosseum, Pantheon, and Baths of Trojan. It describes the Colosseum as an enormous entertainment arena built in the 1st century CE that could hold 50,000 spectators. It discusses the Pantheon as a religious temple built under Hadrian between 125-128 CE, featuring a massive 143-foot diameter dome with an oculus. It also outlines the Baths of Trojan, built in the 1st century CE, which served as a public bathing complex but also included sporting grounds, massage rooms, and libraries.