Exploring throws up all sorts of weird and wonderful abandoned properties. I'd seen this swimming pool numerous times over the years, and was always curious about it. While in France, I had a rare opportunity to pass by, and hopped over the gate to have a quick look.
The pools were part of a nationwide plan to encourage swimming. They were called Piscine Tournesol or Sunflower Pools, obviously enough. 183 were built in the late 1970s/1980s all over France. The original plan from 1969, envisaged 1000 pools across France, following France's poor performance in the 1968 Olympics in Mexico. The first 2 pools were built to the SE of Paris in 1972, on designs by architect Bernard Schoeller. The pool consists of 36 steel arches, of which 12 are retractable to allow a third of the structure to open up in the summer. Today, a 100 are still in situ, with many having been destroyed and a few transformed to a different use. 7 are closed and still in place, including this one, known as Piscine Mai in Douvrin.

Presumably there was additional lighting, as it's pretty dark and bleak inside. This photo took hours of post production, to remove all the crap graffiti tags, and give an idea of how it looked in operation. In the foreground can be seen the remains of where the stalls were for changing.

Some of the uninspiring water based murals, designed to inspire

Unfortunately I didn't have time to remove the tagging in this shot, just the walls. The tagging looks how i imagine dogs see the scents given off when they urinate on common sites.

The wall for the pool containing artwork similar to inside

Here is an shot of one of the pools that has been opened up in the warmer months (taken from here: archipostalecarte.blogspot.co.uk). Note a variation on the design, others include round windows.

Further Links:
A page showing construction of a sunflower Pool barlinsouvenirs.overblog.com
A list of all the remaining pools https://fr.wikipedia.org/wiki/Piscine_Tournesol

Thanks to TheWife and Child for patiently sitting in the car while I nipped off.