My assistant assured me that the remarkable thing about Jumbo was not just its size but that 'it takes you completely by surprise. You walk around a corner not knowing what to expect, and suddenly . . . there it is]'

Jumbo, also known as the Balkan Water Tower, is an enormous example of Victorian municipal engineering, a vast cistern built entirely of brick. Nevertheless, if my assistant's research was correct, it was invisible to the naked eye from most parts of the city. Remarkable.

His research was deeply flawed. We saw Jumbo from the railway station; we saw it from the park; we saw it from the town hall steps. Everywhere we went in Colchester (except under the Roman gateway in the west wall) Jumbo loomed above the trees and rooftops, as if it was expecting us.

They built these towers high to ensure that water could be distributed at a uniform pressure. Above the soaring brick arches was a large square tank; water was dispensed from this reservoir by 'gravity feed'. High up on the roof is a weathervane in the shape of an elephant.

Jumbo was built in 1882 and was named after a popular zoo elephant of the day whose sale to an American circus caused a public outcry.

These days it is obsolete, and stands above the town, largely ignored. When we stood beneath it my assistant fell strangely silent.

Jumbo is at Ordnance Survey Grid Reference TL 993252

(Photograph omitted)