FNRS-3, Preserved bathyscaphe in the Tour Royale gardens, Toulon, France

The FNRS-3 is a bathyscaphe displayed since 1996 in the gardens of the Tour Royale at Le Mourillon, Toulon. Its red rounded hull carries a yellow deck with a central conning tower marked "FNRS III", and a yellow spherical gondola with a dark hatch hangs beneath it on red struts. The vessel rests on two thick grey concrete pillars.

Auguste Piccard's FNRS-2 was damaged in 1948 and sold to the French Navy in 1950. Rebuilt at the Toulon naval base by engineer André Gempp, it was relaunched as FNRS-3 in 1953 under Georges Houot. On 15 February 1954, off Dakar, it dived to 4,050 metres, beating the Trieste's 1953 record by 900 metres.

The initials FNRS stand for Fonds National de la Recherche Scientifique, the Belgian fund that financed Auguste Piccard's stratospheric balloon FNRS-1 and later owned the original sphere. The rebuilt craft kept the name, and its 1954 dive earned Georges Houot and Pierre Willm the Prix Plumey from the Académie des Sciences.

The bathyscaphe stands outdoors in the gardens of the Tour Royale at Le Mourillon, on Toulon's coast, not inside the naval base. It has been displayed there since 1996, so it can be seen without booking a base visit. Look for the yellow deck and conning tower marked "FNRS III" above the red hull and the yellow gondola slung beneath it.

The submersible used an ingenious system where thousands of liters of gasoline in its float tank controlled descent rate through careful water exchange. This clever design allowed operators to adjust depth gradually rather than relying only on mechanical controls.