Fours à boulets des îles de Lérins, Military defense furnaces on Lérins Islands, Cannes, France
The Fours à boulets des îles de Lérins are heating furnaces located on two islands offshore, built to bring cannonballs to extreme temperatures before firing. The structures use brick and stone walls with open chambers where fires reached the bottom of the ovens.
These furnaces were built in the 1790s when the French Navy needed to strengthen Mediterranean coast defenses. They were later updated and remained in service until newer weapons technology made them obsolete.
The furnaces show how the military once used cannon fire to protect the coast and why these islands were vital to French defense strategy. Visitors can observe how soldiers organized their work and what role such installations played in daily garrison life.
Visitors reach the islands by boat from Cannes, which takes about 15 minutes. The furnaces are located on the islands and can be seen with a guide, so wear sturdy shoes for uneven ground.
Hot cannonballs were transported down through a rail system from the top of the furnace before being rapidly cooled in water. This process was so efficient that one furnace could deliver a ready-to-fire cannonball every ten minutes.
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