I'd already visited these amazing drains under the city before, for a party of international drainers. It was a great location and event. However due to the nature of it being a party, I was less interested in exploring and more interested in catching up with those I hadn't seen or even met.

I reached out to some locals, and they were kind enough to meet up and take me down with OllieGT and Alex Residues. The initial attempt to enter the system didn't work out, as my arm was probably about a centimetre too short to flip a bolt. The chaps were cool enough to go the long way around, and let us in. Finally in and able to stand upright, I was able to fully admire the amazing construction of these drains. They were originally natural ditches to deal with the tides, however later they were used for sewage. This lead to the inevitable issues connected to open drains, and as such they were covered up. Landowners were given the incentive of more land by covering over the drains. As such, one can see lots of different approaches to the covering of the drains. The pic below is off a large chamber area, not far from an entry point for official tours.

One of the drain passages disappears off from the main chamber, seen above.

Here can be seen the various attempts by landowners to brick over the drains, at least 4 can be seen here. The initial one at the top of the picture, a darker coloured brick roof, a white brick that isn't a natural arch, and a more regular arch. All made from bricks, that are rather small compared to normal. The sewage runs in the metal pipes now.

Another longer tunnel that wasn't covered over by landowners, or maybe landowners grouped together and employed the same builder.

Here a more triangular styled roof has been built, and an arch shape can just be seen in the background. The floor has also been reinforced along with the sides.

A more industrial looking section, the variety in the system is quite remarkable and definitely a treat on the eye.

Here an interestingly reinforced section at a split.

A more traditional egg shaped sewer, lurking behind a weir wall. Time didn't allow for us to explore it, another day perhaps.

I was told about a section that had collapsed in the 1920s, looking at the concrete reinforced nature of this section, it might have been here. The lack of brick meant we kept moving, concrete is just not sexy or interesting.

A final shot of the ever changing layout here, this being an almost fully triangular shaped tunnel, something I've never seen before, in person or online.

The system runs for quite a way, and we only saw a small section. However what we saw was truly brilliant, not just from an aesthetically pleasing point of view, but also the clear historical nature of the drains. Big thanks to Ben, Joachim and Rouille D'anvers.