Poros is a beautiful island that looks like it could be connected to the mainland. It is just 360m from Galatas on Peloponnesos at its narrowest point. It is actually 2 islands that are joined by an isthmus. Kalavria is in the north, and Sfairia, where Poros town is located, is to the south. The town is a great place to walk around.
Poros doesn't have much as far as ruins, but the remains of the Temple of Poseidon where the orator Demosthenes committed suicide in 322 BC. The population was sparse throughout history until Greeks from Turkey arrived in the 1920s.
I only stopped for a short time and walked around town. I will have to return to see the rest of the island.