The word Baroque means a misshapen pearl. This period of architecture was called baroque because it was considered very odd. Baroque architecture evolved out of Renaissance architecture in Italy. In the 1600's, the renaissance architects began to get bored with the symmetry and same old forms they had been using for the past 200 years. They started to make bold, curving, and not at all symmetrical buildings, with ornate decorations. They started to make curving facades, and used the double curve (in at the sides, out in the middle) on many different buildings.
The baroque architects used marble, gilt, and bronze in abundance. Baroque pediments (triangular area between the rooftop and the end of the roofs) were often highly decorated, or interrupted at the center. The tips were sometimes turned into scrolls and gilded. Many of the ceilings used something called illusionism. That is when paintings are elaborately done, to make it look like the painting is actually an engraving, or protrusion on the wall or ceiling. Baroque art and architecture was often used to express emotion, and was very elaborate. It was popular mostly among the upper class.
The most distinct shape of the Baroque style is the oval. It was a very common shape among baroque buildings. Creating buildings out of complex interlacing ovals allowed the architects to have large open spaces that were different than just plain circles. The domes on many churches were oval shaped, but some were circular. That posed a problem because manly ceiling spaces were oval shaped. To accomplish putting a circular dome on an oval space, the architect had to use very strange angles, but it did create space for sculptures and paintings.
Two main architects of the baroque era were Bernini and Borromini. Bernini's first medium was sculpture. He liked to incorporate lots of it into his buildings. A sculptor and mason, Francesco Burromini went to Rome in 1614, and trained under Bernini and Carlo Maderna. Lots of Borromini's buildings incorporated many shapes and different forms.