3. The Pantheon
Originally built by Marcus Agrippa in 25BC, the Pantheon served as a temple to the many gods of Rome. After the great fire of 80AD Pantheon was rebuilt by the emperor Hadrian. In 7th century the Pantheon was converted to a Cathholic Church and was used as a burial place of famous figures and Italian kings. The Pantheon is well preserved which is not an easy task since its construction is very fragile. It consists of columns, walls and domed roof with an oculus, i.e. central opening. Doom is made only of concrete being a daring engineering experiment.