This cast iron aqueduct, known as Cosgrove Aqueduct, was built in 1809-1811 by Benjamin Bevan. It carries the Grand Union Canal across the River Ouse (just out of shot to the bottom right). The Grand Union Canal runs from London to Birmingham. An earlier aqueduct at this site collapsed in 1808.

As you can see, the aqueduct received a new paint job in 2011 to mark its 200th birthday. I can’t find a source for this, but I remember reading that when the canal was drained to inspect the structural integrity of the aqueduct, a Wellington boot was found wedged into a small hole, plugging it from leaking…

The smaller tunnel to the left is a horse tunnel or cattle creep, which allows animals - and humans - to get through beneath the canal. Being primarily for animals, it’s a bit of a squeeze for humans.

I’m 6’1” - and not the biggest fan of tunnels and confined spaces! - and whenever I have to go through, I tend to spend as little time as possible ducking under the dripping, dark masonry. Taking a bicycle through only makes the tunnel more narrow.

I’ve made this trip enough times now that I can do it without too much worry, but I still get a bit freaked out in a running-up-the-stairs-at-night kind of way!

Sources: Canal and River Trust; Wikipedia