万神殿, or the Pantheon, is a former Roman temple located in Rome, Italy. It was completed around 126 AD during the reign of Emperor Hadrian. The structure is renowned for its large dome, which remains the world's largest unreinforced concrete dome. The Pantheon is dedicated to all the gods of ancient Rome. Today, the Pantheon serves as a church known as Santa Maria ad Martyres. It is one of the best-preserved ancient buildings and has influenced architecture throughout history. The building's oculus, an opening at the dome's center, allows natural light to illuminate the interior, creating a unique atmosphere.