Lysimachia is situated in the Prefecture of Aitoloakarnania. It covers an area of 13,2 Km², it is about 17 km wide, and has a maximum depth of 9 meters. The river of "Ermitsa" spills into the lake and at the same time the waters of the lake find their spillway to the river of Acheloos.

The river of Lysimachia, along with the river of Trichonida, is part of a unique ecosystem. Its shores are filled with canes and are home to a variety of migrating birds during the winter, such Coots (Fulica atra) and Mallard ducks (Anas platyrhynchos). Other birds also nest in the area, such as the Purple Heron (Ardea purpurea), the Little Bittern (Ixobrychus minutus) and the Black-crowned Night Heron (Nycticorax nycticorax). The lake ecosystem also features a vast range of fish species and the rare European otter (lutra lutra). 

In the past, the "twin" lakes of Lysimachia and Trichonida were united in one large lake and constituted a rich ecosystem.  According to some written descriptions of 19^th-20^th century travelers, around the lakes there was a dense forest. Nowadays, the two lakes are connected through a canal and are crossed by the national road of "Antirrio-Ioannina".