The Teatro di San Cassiano is recognized as the first public opera house in Venice, Italy, opening its doors in 1637. It marked a significant development in the history of opera, allowing a broader audience to enjoy performances. The theater was built on the site of an earlier structure and could accommodate around 1,000 spectators. Designed in the Baroque style, the Teatro di San Cassiano featured a proscenium arch and elaborate stage machinery. It hosted numerous operas, including works by notable composers such as Claudio Monteverdi. The theater played a crucial role in popularizing opera as a form of entertainment in Europe.