The island of Agios Achillios sits in the middle of Micro Prespa and is reached by a wooden pontoon bridge from the village of Psarades — about 150 metres of planking across the still water. The island holds the ruins of a large 10th-century Byzantine basilica, the remnants of a medieval town, and a small number of permanent residents.
The basilica ruins are among the most atmospheric in northern Greece — three nave walls survive to considerable height, stone-built and roofless, surrounded by grass. The island is quiet and beautiful, and the short walk from the bridge to the ruins takes less than 15 minutes. The annual Prespia Festival is held here in late August, with performances against the backdrop of the ruins.