page_title: Lock (water navigation)
section_title: Round locks
hierarchical_section_title: Lock (water navigation) / Special cases / Round locks
caption_attribution_description: Français&#160;: Agde (Hérault) - Bassin rond et ses trois portes du Canal du Midi.English: Agde (Hérault) - Round basin and its three Canal du Midi gates.
context_page_description: A lock is a device used for raising and lowering boats, ships and other watercraft between stretches of water of different levels on river and canal waterways. The distinguishing feature of a lock is a fixed chamber in which the water level can be varied; whereas in a caisson lock, a boat lift, or on a canal inclined plane, it is the chamber itself that rises and falls.
  Locks are used to make a river more easily navigable, or to allow a canal to cross land that is not level. Later canals used more and larger locks to allow a more direct route to be taken.
  Since 2016, the largest lock worldwide is the Kieldrecht Lock in the Port of Antwerp, Belgium.
context_section_description: There are several examples where locks have been built to a round plan, with more than two exits from the lock chamber, each serving a different water level. Thus the lock serves both as a way of changing levels and as a junction. The circular plan of the lock allows boats within it to rotate to line up with the appropriate exit gate.
  The best known example of such a round lock is the Agde Round Lock on the Canal du Midi in France. This serves as a lock on the main line of the canal and allows access to the Hérault River.
  A second French round lock can be found in the form of the, now disused, Écluse des Lorraines, connecting the Canal latéral à la Loire with the River Allier.
caption: Agde Round Lock
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