El Ojo del Canal (The Eye of the Canal)

El Ojo del Canal is an aqueduct on the Imperial  Canal of Aragon, one of the most important canal projects constructed in Spain.

 Because of the desire to save money canal builders usually  narrow the canal width  across the length of the aqueduct,  to the width of only slightly wider than  one boat. On this, 68 mile long, late 18th century, canal,  however, navigation was a secondary concern. Its main function  was as an "acequia" with the main requirement being to transmit irrigation water from higher reaches of the Ebro, as effectively as possible. The Ojo del Canal aqueduct in Zaragoza, Spain,  was thus constructed at full canal width to carry the canal waters over the Rio Huerva with minimal impediment to flow.

  The canal is carried over the valley  on an impressive  single elliptical arch with an opening 30 feet wide with the canal carried about 60 feet above the river. The construction  was of masonry, mainly limestone, and the historic  pictures show it to be an impressive  structure. The "eye" shape of the void through which the river flows is believed to have given rise to the name.

Unfortunately, in the 20th century, roads were constructed either side of the canal between the Cassablanca lock complex and a point just downstream  of the aqueduct (as a one way system for vehicles).  The bridges carrying these two roads over the Huerva were placed close alongside the aqueduct allowing pedestrians  at road level only able to get a view the aqueduct  through a narrow  slot on the  eastern  side of the structure. In fact, because the canal does not narrow,  if you were to walk past the aqueduct on one of these two modern road bridges you could easily miss the fact that an aqueduct was there at all. It does not change its width and the roads stop you getting  the impression  that you are above a river valley. Growth of trees on the river banks mean that you need to get quite  close for a view of the arch.

What does identify the aqueduct is the presence on the eastern bank of the canal of a small building marked above its door " Almenara del Nostra Señora del Pillar". This historic structure houses a control gate system  that can rapidly  release canal water down a steep spillway  into the river when canal levels are becoming   high, as a means of preventing overflow of the aqueduct or down stream flooding. It is not clear whether release of canal water into the river would also be used to supplement river water flow in times of local droughts.

As the Passeo de las Reys de Aragon, on the eastern side of the canal, passes the building it turns to the  left to become Passeo de Colon and between this road and the river is a small (unamed)  park containing  an outdoor gym. The park also contains information  boards (in Spanish but with some excellent images) about the aqueduct and the park also provides a (quite difficult)  access to the river which can afford a better view of the aqueduct's engineering  (which is impressive  for it's time).