Aqueducts
In Rome, sometimes they made aqueducts to transport water from the source to the city. In a lot of parts in Europe there are aqueducts.
This is the aqueduct of Massanella (Mallorca). It is difficult to see it because it is camouflaged between the rocks.
The Romans built very big buildings. The most popular buildings for them were temples, theatres, thermal baths, amphitheatres and, of course, aqueducts.