The prison where Alfred Dreyfus was held, Devil's Island,  is just offshore of this polity.  
Massif Decou Decou, Mount Saint-Marcel, and Mount Itoupe are smaller mountains in this polity.  Most of this polity's borders are formed by rivers, including the Oyapock, Lawa, and Maroni rivers.  Its largest body of water is formed by a hydroelectric dam and is named Barrage de Petit Saut.  In the 19th century, it fought with (*) Brazil over Counani, a small short-lived independent state, and in the 1970s this nation was home to refugees from Laos, prompted by the  ? French government.  The prison where Alfred Dreyfus was held, Devil's Island,  is just offshore of this polity.  For 10 points, Cayenne is the capital of what French overseas department?
Massif Decou Decou, Mount Saint-Marcel, and Mount Itoupe are smaller mountains in this polity.  
{French Guiana}