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Origin and history

The Agde Round Lock is an unusual lock of the Canal du Midi, designed in the 17th century to connect Agde to the river network. Unlike the traditional two-door locks, it has three, allowing the boats to choose between three distinct directions: towards Béziers via the lock of Portiragnes, towards the pond of Thau by the upper course of the Hérault, or towards Agde via the lower course of the Hérault. Its round structure, built in 1676 in black basaltic stone, initially allowed fluid maneuvers in a 29.20 metre diameter and 5.20 metres depth. The three doors opened on different water levels, illustrating advanced hydraulic engineering for the time.

Originally, the lock was surrounded by a set of functional buildings, including an administrative building, stables, shops and a chapel, reflecting its central role in local activities. Although its round shape was modified during enlargement work in 1978 to fit the Freycinet gauge (allowing the passage of barges up to 38.50 meters), it remains an exceptional testimony of the genius of Pierre-Paul Riquet, engineer of the Canal du Midi under Louis XIV. This three-tier system, dated from the 17th century, is part of the broader project of the Languedoc Canal, completed in 1682, to link the Atlantic with the Mediterranean.

Agde's Round Lock has been listed as a Historic Monument since 1996, recognizing its heritage and technical value. It shares this architectural singularity with only one other round lock in France, that of the Lorrains, now downgraded. Its precise address, 2 Avenue Raymond Pitet in Agde, and its integration into the river public domain underline its importance in the historical and tourist landscape of Occitanie.

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