Twenty-five km on the southeast of the archipelago, Marie Galante is the biggest of the satellite-islands. Essentially rural, it's a limestone plateau not very elevated in height, but surrounded by stunning beaches and some dramatic rocky cliffs. The main village is on the southern coast, Grand Bourg, and it is where you will arrive by ferry. There are some stores, cute boutiques and restaurants open during the day, but except from the street facing the harbor, it is fairly deserted during the night. I recommend visiting at least the main cathedral and the lively market square in front of it, and if you're lucky, to spend some time on the Plage de Grand Bourg - when we were there it was infested by sargassum.
We spent most of our time on the island in the area of Saint Louis (a ten minute drive from Grand Bourg), where our bungalow was and the most fabulous beaches are. The village is tiny and modest but has a nice dock (with a monument dedicated to the fallen sailors), some traditional colorful houses and a very good local bakery We ate twice at this good restaurant literally on the beach because all the other ones were closed during Easter week. There is also a convenient supermarket that closes during lunch but has all you need for dinner or a picnic. The coast from there to the north is composed by half a dozen stunning beaches, among which lays Anse Mays - our favorite one, a true paradise, especially because when we were there we had it almost all for ourselves! Right attached there is Plage Moustique (also a little narrow, and by the road) and, on the Chemain Vieux Fort, the more famous Plage de l'Anse Cannot, definitely superbe, but the most visited, also by boats. From there you can walk through the path (or continue on the Chemain du Vieux Fort) to another amazing beach, Plage du Vieux Fort, also incredibly beautiful (the ocean there seems a little rougher there but the snorkeling was amazing) and practically deserted!
On the southern side of Saint- Louis there is also the long beach of Anse de la Frais or Plage des Trois Îlet, named like this because from there you can see the three islands of Dominica, Basse-Terre and Les Saintes. Our bungalow owners, Sylvie and Philippe, suggested us to go there at the sunset and it wasn't disappointing!
We drove all around the island and stopped to see the Gueule Grand-Gouffre, a big, almost perfectly round depression on the cliffy coast and then at the old and beautiful Moulin de Bézard, near the more famous Moulin de Bellevue, which was closed when we got there because part of a private distillerie, Habitation Bellevue.
The oldest site on the island is though the Habitation Roussel-Trianon near Grand-Bourg, located on a beautiful history-themed park, and showing the very interesting, but also sad cultural and colonial heritage of Marie-Galante, together with the mansion of the Habitation Murat (which we didn't have time to visit). Besides of all the mills, another special feature of this island, and a pretty picturesque one, is the presence everywhere of the boefs-tirants, pulling-bulls, with a very prominent role also in many competitions!
Unfortunately, the area around Capesterre has been heavily affected by the sargassum: one that is supposed to be the most beautiful beach of the entire archipelago, Plage de la Feuillere is now almost all covered by smelling weeds now and this has sadly impacted (at least during the spring) all the tourism there.
This website, this one, and this one have all the things that you can do or see in Marie-Galante, in French!