Following The Aqueduct Out Of The City

The great arched aqueduct crossing a valley on the city's edge is the visible fraction of a much longer structure. Following its line outwards is one of the more legible day walks in the region.

The arches are the small part of the system

What most people see is the section spanning a valley, because a valley crossing has to be built up on arches. The rest of the channel runs at or below ground level.

An aqueduct is a gently falling conduit. It only rises into arcades where the terrain drops away, so the dramatic sections mark the low points rather than the important ones.

The consequence is that the structure continues for many kilometres inland as culverts, buried channels and low walls that are easy to walk past without noticing.

The route was decided by gradient

Water moves by gravity alone, so the channel must fall continuously and very slightly along its entire length. That single constraint determined the whole alignment.

Rather than taking the shortest line from spring to city, the channel contours around hillsides, holding a shallow fall. It wanders because the ground made it wander.

Which is why walking beside it is unusually pleasant. You are following a route engineered to be almost level across country that is not.

Springs, not a river

The supply came from springs in the hills inland rather than from the estuary, because the estuary is tidal and salt and the local wells were unreliable in a dry summer.

Several collection points feed the main channel, each with its own small structure over the source. These are scattered across the countryside and are part of what makes the route interesting on foot.

The system also included covered reservoirs at the city end, built as large stone chambers where water was held before distribution to public fountains.

Walking it takes planning rather than fitness

The line crosses roads, private land, suburbs and open country in sequence, so it cannot be followed continuously. Most people walk sections and connect them by train or bus.

The urban sections are straightforward and can be done in a morning. The rural sections need a map, water and an understanding that the path is not signposted throughout.

Summer is the wrong season for the open stretches, which have no shade. The cooler half of the year suits the walk far better.

What the structure says about the city

A city that builds a stone channel across many kilometres of hill country is a city that has already outgrown its local water, and the project reflects that pressure.

It also survived the great earthquake largely intact, which is why the structure is treated locally as much as a piece of engineering pride as a monument.

Seen from inland, the arches read differently than they do from the city. They are the last stage of a long rural system rather than a monument at the edge of a suburb.