I want to know the answer to the following question:
What was knocked down in 1866?
All the background I'm provided with is that "The public water supply network was completed in 1850, and in 1858 the architects Sebastián Monleón Estellés, Antonino Sancho, and Timoteo Calvo drafted a general expansion project for the city that included demolishing its ancient walls (a second version was printed in 1868).". Is that enough to answer the question?
Answer: no