The Giens peninsula is especially remarkable because it is connected to the mainland with a double barrage, called tombolo. Giens was long ago an island, but by the flow and the sedimentation a double barrier was formed and connected it to the mainland. It is however quite exceptional that here a double barrier was formed.
Between the two barriers there are salt fields (but no longer exploited) and a lake (l'Etang des Pesquiers). The lake is home to a colony of pink flamingos. Depending on the season up to 1500 may be counted. To see them you have to go to the parking lot at the end of the barrier (side Giens) and walk a little way on the barrier. This eastern barrier is indeed now closed to traffic. Have a look at the other side. In windy weather this bay is very popular with kite-surfers who perform spectacular feats on the high waves.
For a good view of the barriers you best go to the center of Giens (on the island). On the ruins of the Chateau de Giens (dating from the 13th century) is an orientation table where you have a panoramic view.
In Giens also have a look in the church.
The Sentier du Littoral runs around the whole island and also has a bifurcation to the Centre of Giens. If you're staying in the neighborhood, this tour is,, definitely worth the while, even for a multi-day trip (considering the length.