It was built in the 18th century in Neoclassical style after the original great Lisbon opera house in Comercio Square was destroyed in the Great Earthquake.
The exterior was inspired by Milan's La Scala, and the beautiful interior (with excellent acoustics) is similar to the San Carlo Theater in Naples, with five galleries and boxes adorned with neoclassical and Rococo decorations.
There is a very pleasant restaurant with tables on the pavement outside.
http://www.golisbon.com/sight-seeing/sao-carlos-theater.html
