When the Romans settled in Spain and founded Barcino, one of the first important works they did was to supply water to the city.
This infrastructure was carried out by using water tanks and wells and two aqueducts that brought the water from the river Besòs and from the Collserola mountain. Both aqueducts got together and converged on the Roman wall in the Gothic Quarter.
This water was used for domestic use and for public toilets. The used water was expelled to the sea trough a sewage system.
They have not discovered remainders of the first aqueducts system yet. Remainders of the second system can be seen in Cathedral Square (a reconstruction was done by the city of Barcelona in the s. XX), near the Roman wall. At the foot of this Aqueduct, you can see a work of the Catalan artist Joan Brossa: the sculpture that say “Barcino” the name that was founded the city of Barcelona.
Other remainders recently discovered in 1988 thanks to the demolition of a building just steps from here: in the street Duran i Bas. This aqueduct is part of the structure of a building that was constructed several centuries later. It is around 8 meters higher and it is preserved in relatively good condition, considering that it is more than 2000 years old.
Free entrance: Every day
Location: Plaça Nova, Barcelona (view map)
Metro: L3 (Plaça Catalunya) or L4 (Sant Jaume)
More gratis: http://www.guesthousebarcelona.com/gratis-barcelona.htm