The monumental architectural achievement built to honor the emperor in ancient Rome is the Pantheon, originally commissioned by Marcus Agrippa during the reign of Augustus but later rebuilt by Emperor Hadrian around 120 AD. The Pantheon is renowned for its impressive dome and oculus, symbolizing the majesty of the Roman Empire and the connection between the divine and human realms. It served as a temple dedicated to all gods, showcasing advanced engineering skills and artistic design. The structure remains remarkably preserved and continues to influence architecture through its innovative use of space and light and its blend of classical elements, embodying Roman ideals.