Saturday Photo: Roman Walls at Conímbriga, Roman Concrete Lasts

This week I sent of the revisions to my next book: Rock of Ages: How Concrete Built the World as We Know It. The University of Regina Press will bring it out in 2020.

This is one of the photos I'm suggesting we use.  It's of a Roman wall built in Conímbriga, Portugal, not far from the university town of Coimbra.  Dating from the Third Century CE, it was built on the far western frontier of the Roman Empire, but it still stands.  As such it's a tribute to the many, many Roman constructions that used their rather wonderful concrete, the secret to which was lost for about 1200 years after the Fall of Rome. 

You'll notice that this wall doesn't look like a modern concrete wall wood: the concrete wasn't poured into forms to cure.  Rather, the Roman usually built walls like this with a stone exterior and a hollow interior into which rubble and their concrete were dumped.  In many cases the stones have succumbed to the ravages of time, but the concreted interior survive.