Art is made of constraints. When architect Frank Gehry received a commission to build whatever he wanted, he turned it down. Sometimes, artists create their own constraints. The French writer George Perec wrote a 300-page novel, “La Disparition,” without using the letter “e.”

Other times, circumstances dictate the constraints. When artist Joana Vasconcelos was invited to represent Portugal in the Venice Biennale, the problem was that Portugal does not have a permanent pavilion at the fair. The artist’s solution was to use a ferry boat that was about to be dismantled both as a floating pavilion and exhibition piece. So, after spending a lifetime between the margins of the Tagus river, this humble boat has become a work of art!

The ferry boats that cross the river Tagus are called “cacilheiros.” They’re a great, inexpensive way to travel on the Tagus. Click here to see their schedule.