Aqueduct of The Miracles (at Emerita Augusta), at Merida, Badajoz.
Dyke of Proserpina cistern is 425 m. long and 20 m. high. ITs constructed with a central structure of concrete "opus caementicium", reinforced with stepped granite ashlars, little ashlars or masonry depending on the area. A surface of earth at its exterior side was limited by a contention wall. There are also inner and outer buttress.
It begins with an underground section with a vaulted masonry gallery of brick. It is 2 m. high and 1 m. wide and ends at a pool that makes the whole conduction enter to an area elevated by archs.
Course of this high section -more than 825 m. long-, is divided in many parts defined by the different directions it takes. Pillars have a square plan. Each side is 2,5 m. long. It is built with ashlars and bricks, five files of each material with a concrete inner. Sometimes concrete invades room of ashlars to consolidate unity of construction, that bears masonry at the exterior side. Ashlars are joined by wooden staples. As they become higher, there are buttress elevated on their lateral sides. Archs are made of brick except the central inferior of those that are over the river: it is composed by 9 stone voussoirs.
First section, i.e., before first angle, is composed by three rectangular pillars. Third one had a basement so spoilt by loss of ashlars than it named "The Miracles" -Los Milagros- the whole construction. Today it has been restored because of a danger of fall.
Second section is the major one. It is found at a certain distance from the three pillars already mentioned. All pillars are reinforced with butterss. At the area over the river there are cutwaters. Just at this place we find the major level of the aqueduct 25 m. high. It would be higher if there have existed the "specus" and a supposed passing by gallery. All this section shows three levels of archs built with bricks, except the central one -as has been said- made with stone voussoirs.
Remainings from the third section are also separated: they marked a clear angle with the direction of the prior. First pillar is the most solid because of its function of changing conduction direction. Direction goes to the city and its highness diminished little by little.
The whole construction ended at a square plan tank called "castellum aquae". Its side was 6 m. long. It was made with concrete and ashlars covered by marble.