A visit to the archaeological site of the Sant Antoni market allows us to observe a rectangular opening in the wall called the counterscarp, which is the one that delimits and closes the moat on the outside. This opening is the exit of an underground gallery of certain dimensions and it is a collector that collected the water that accumulated on the outside of the wall, on the Creu Coberta path.
According to Emiliano Hinojo, the archaeologist who directed the excavations, some 28 meters of the collector gallery were preserved, which crossed the glacis, which is a sloping area of accumulated earth just after the moat. Their mission was to expose the attackers, who were thus exposed to the weapons of the defenders.
The market reform works exposed what had been the Sant Antoni bastion, whose moat is the currently accessible area below street level. The collector had no defensive function, just to prevent the accumulation of water beyond the glacis. The water was led into the ditch, and fell on a rectangular tiled floor, which is also preserved at the foot of the collector outlet. Thus, soil erosion of the ditch was prevented.
There are documentary references to this collector in 1682, when maintenance work was carried out on the outside of the wall, but it is to be assumed that its construction must have been at the time the Sant Antoni bastion was erected. The works began in June 1644 and were part of a broader set of improvements to the Barcelona wall as a consequence of the progressive improvement of firearms and in the time frame of the conflict with France in 1635 and the Guerra dels Segadors (Guerra dels Segadors 1640-1652).
The collector was canceled during the 18th century by covering the opening in the counterscarp of the ditch.