Roman architecture was heavily influenced by Etruscan and Italian traditions, however, it was primarily influenced by Greek Architecture. Eventually when Rome grew politically, they developed their own style of architectural design. Romans used many different materials to build. The most popular material used was mud brick strengthened by timbers. Hard limestone and Volcanic Tufa were used for terraces, fortifications, foundations and superstructures. Eventually, Romans began using Travertine because it was stronger as well as large varieties of marble. For roof tiles and as protective covering for wooden parts of buildings they used terra-cotta. The use of this material declined as stone temples became more abundant in the 3rd century BC. From the early empire on, baked bricks began to be made and used in large quantities. In the 2nd century BC an unusually strong cement, that included a volcanic dust called pozzuolana, was used more than the traditional materials. It was a more durable and economical material, and was used in their buildings, roads, and bridges. An example is the Pantheon, an architectural masterpiece of ancient Rome. It was completed in 126 AD during the reign of Emperor Hadrian who may have helped design it. The Pantheon is a circular building topped by a dome. A 100 foot long rectangular porch stretches across the front. Over the porch is a triangular roof supported by 16 Corinthian columns of granite, each 42 feet high. Throughout the republic the temple design basically remained Etruscan. It was top heavy with wide eaves and terra-cotta decorations. In the second century BC local traditions and Greek forms came together to create a more graceful structure. The podium and deep front porch of the Etruscan temples were used along with Greek proportions. This fusion of Greek and Etruscan designs can be seen in both public and private constructions. An example of this in a civic building was the Basilica which was a multipurpose rectangular hall. The Basilica first appeared in Rome in the 2nd century BC and was usually placed in the town forum. An example of a domestic building was the simple Etrusco-Italic town house. It had rooms grouped axially around a dark central hall (atrium) with a range of single-column colonnades around a rear garden. Another example of a domestic building is a country villa. They were built to serve well to do persons as either working farms or as retreats for relaxation. Some villas display symmetry while others are less colonnaded or vaulted. Even though the Romans copied some Greek architectural forms after they conquered Greece, they achieved architectural greatness in their own rights. Roman builders knew how to construct huge arches and vaults, and roof their buildings with semicircular barrel vaults. Brick, strengthened with concrete was a favorite building material in ancient Rome. This material gave such durability to their constructions that many of their creations are still standing today.