“Well that was strange and unintelligible” said R as we returned to the car.

On our way out of Albarracin, we made a quick stop to view a section of the Roman aqueduct that connected the Rio Guadalaviar to the town of Cella, some 25 km away. At this viewpoint, the Barranco de Burros, it consists of a series of rock tunnels lining a canyon, with windows cut for ventilation and maintenance access. One can now hike past the modern retaining wall (protecting from flash floods in the gully) to access the tunnel system. You can walk, not quite upright through them, and marvel at the labor it took to plan and build 25 km of it.

Modern estimates are that this viaduct carried 16 gallons per minute. This massive undertaking was used for centuries. No one knows for sure when it was abandoned, but there is, per the signage, no mention of it in Christian records from the reconquest of Cella (one end of the aqueduct).