Pointe du Grouin du Cou lighthouse, Lighthouse in La Tranche-sur-Mer, France.

The Pointe du Grouin du Cou lighthouse is an octagonal concrete tower with a black lantern standing at the entrance of Pertuis Breton. It sends colored light signals at regular intervals to guide ships safely through the local waters.

An earlier lighthouse was built here in 1831, but it was destroyed in 1944 during World War II by German forces. The current tower was constructed in 1953 following a design by Maurice Durand.

The tower is also known as the La Tranche-sur-Mer lighthouse, and it marks the entrance to the Pertuis Breton off the Île de Ré. Its light shows white, red or green depending on direction, a supplementary green sector having been added in 1931. The site is government property and closed to visitors.

The lighthouse sits on France's western coast at the entrance to the Pertuis Breton bay and can be viewed from several viewpoints along the shore. Keep in mind that it can only be seen from outside and sits directly by the water.

The tower's light comes from a Sautter-Harlé lens with six cut-glass panels and a 0.30 m focal length, producing 120,000 candelas. Its flashes are visible across 360°, and the signal shows white, red or green depending on the direction. The optic is halogen powered.