South of Messinia, in the open sea of Methoni, we come across the Messinian Oinousses island complex, comprising Schiza, Sapienza, Venetiko, Aghia Mariani (Aghia Marina), and the islets Avgo, Dyo Aderfia and Boba. The Messinian Oinousses, along with Cape Akritas, have been included in the Natura 2000 Network, with code GR2550003. The deepest point of the Mediterranean Sea is located south of the complex, and it is known as the "Shaft of Oinousses;" 5,121 m. deep, this is where research connected with the NESTOR experiment (Neutrino Extended Submarine Telescope with Oceanographic Research) takes place. The aim of this experiment is to detect neutrinos, the almost immaterial, invisible particles, which are believed to hold significant information about the universe's past and future.
The complex's two larger islands are Schiza and Sapienza. Schiza has an expanse of 12 km2 and it is known for the cave of "Mavri Troupa" ("black hole"), located on the western part. The cave has not been explored, a fact that rouses the imagination, providing fertile ground for stories surrounding its former use: Could it have been a pirates' lair? We might never know. Sapienza is the second largest island, expanding across 9 km2. It is a verdant island, with rare and interesting flora and fauna. Here we will find the unique in the Mediterranean arbutus forest, with trees that exceed 10 m. in height. The great zoological importance of the region is indicated by the presence of 23 major kinds of vertebrates, among which the bottlenose dolphin (Tursiops truncatus), the Mediterranean monk seal (Monachus monachus) and the Caretta caretta sea turtle. Sapienza is also home to the Cretan goat (kri kri), which was brought to the island in great numbers, in order to protect the species from extinction; there are also mouflon wild sheep, and many bird species. Another interesting site on the island is the plateau found at its center, which was formed by the deposition of pollen across many thousands of years. Spartolakka, as the plateau is known, is a great source of information for scientists, helping them to date the forest and the surrounding area.