The Peninsula Castle is the older and less-visited of Trakai's two castles, its ruined walls rising from a promontory between two lakes near the town centre. Built in the second half of the 14th century — before the Island Castle was completed — it served as the main ducal residence until the island fortress superseded it.
The ruins today are substantial: sections of wall several metres high, the bases of towers, and the outline of the courtyard. Unlike the fully restored Island Castle, the Peninsula Castle is left in its authentic ruined state, which has its own melancholy character. The views from the promontory across the lake system are excellent, and the relative absence of visitors compared to the Island Castle makes it a peaceful alternative.