The cistern that became a pool
Every house of this kind had one: the roofs drained into the courtyard, the courtyard drained into a cistern under it, and that was the household's water from October until the following summer. Nîmes has a Roman aqueduct running past it and still built cisterns, because the aqueduct stopped working in the sixth century.
The mains arrived on the rue de l'Aspic in 1954. The cistern was capped and forgotten, and when the conversion opened it up in 2007 it was full of rubble, three bicycles and about four hundred litres of water that had got in from somewhere.
Turning it into a pool was not cheap. The stone lining had to come out and go back in, and the vaulted top was removed and the edges carried on a new ring beam. The whole thing then had to be tanked without anything modern showing at the surface.
The architect's estimate was eleven weeks. It took seven months, and by the end of it the owners were being asked, politely, by two separate contractors whether they had considered filling it in and putting a pool somewhere else in the court.
What they got for the trouble is eight metres by four of cold water lined in stone that has been underground since about 1760, with the original overflow channel still cut into the paving and still doing its job when it rains hard.
The pool is unheated and will stay that way, because a cistern is meant to be cold.