The longest Roman aqueduct was Constantinople.

An Aqueduct is the answer. And to embellish this a bit more, I believe there is an aqueduct in Rome that still functions. Perhaps it has been closed down, but years ago when I was a student studying ancient Rome, the aqueduct was working.

If you are referring to making a model Roman aqueduct, you can find websites which tell you.

The main purpose of Roman aqueducts, or any other aqueduct for that matter, is to transport water.

The main purpose of Roman aqueducts, or any other aqueduct for that matter, is to transport water.

The main purpose of Roman aqueducts, or any other aqueduct for that matter, is to transport water.

The main purpose of Roman aqueducts, or any other aqueduct for that matter, is to transport water.

The main purpose of Roman aqueducts, or any other aqueduct for that matter, is to transport water.

The main purpose of Roman aqueducts, or any other aqueduct for that matter, is to transport water.

The main purpose of Roman aqueducts, or any other aqueduct for that matter, is to transport water.

The main purpose of Roman aqueducts, or any other aqueduct for that matter, is to transport water.

The main purpose of Roman aqueducts, or any other aqueduct for that matter, is to transport water.

The Segovia Aqueduct in Segovia, Spain is the best preserved Roman aqueduct still in existence. Its importance is shown by its appearance on the Segovia coat of arms.