The "Round" lock at Agde - 3 entries/exits, on the Midi Canal

The Round lock at Agde

The "Round" lock at Agde

There are three entries/exits to & from this lock, hence the need for it to be "round" to enable the barges to turn and select their choice of route. To the left are Béziers, Narbonne (& Port la Nouvelle) and Carcassonne. To the right are the River Hérault (above the Weir) and the Étang de Thau with a multitude of towns on its shores all specialising in shellfish from the étang, and at the far end the Mediterranean port of Sète and the end of the Midi Canal. Heading south brings you once again to the River Hérault but this time below the Weir, giving access to Grau d'Agde & the Mediterranean.
For some boathire companies the "round" lock is as far as their boats are permitted to go, remember some canal boats are shallow draught and not very suitable for the Étang de Thau which can get quite rough very quickly!