Alonnisos
If you ask someone in Greece to name the most eco-friendly island, they would most likely tell you it's Alonnisos. Situated 40 kilometers south of the Pelion peninsula, Alonnisos belongs to the group of lush green islands called the Sporades, which lie idyllically in the Northern Aegean.
One the boat approaches the port of Patitiri on this relatively quiet island, you will be immediately be struck by the lush greenery, magical cliffs and transparent waters. This is an ecological haven that's been claimed by monk seals, dolphins, wild goats and other rare species. It is home to the Natural Marine Park of Alonnisos, and boasts active centers for the Hellenic Society for the Study and Protection of the Monk Seal (MOM), both acting as a hub for environmental awareness and conservation.

The harbor town of Patitiri is considered the 'modern' town, built after a massive earthquake destroyed the older main town, Palia Alonnisos, in 1965. Luckily, the original village, also known as Palio Chorio, has been rebuilt and maintains its amazing traditional architecture. Little charming hotels and restaurants dot the village, along with colorful boutiques a couple of patisseries and coffee shops with some of the most amazing views. The new main town of Patitiri also has its attractions, such as the Alonnisos Museum, harbor tavernas, and a permanent exhibition for the Monk Seal initiative, MOM. Within walking distance is Rousoum Yialos with a crystal clear pebbly beach, featuring a couple of restaurants and coffee shops.
Apart from the two main towns there are a handful of sparsely populated settlements or villages that offer amazing seafood, beaches and attractions. Steni Vala is a quaint fishing village with a clear, calm beach surrounded by verdant hills. Apart from its lovely cafes and good food, there is the MOM station that takes care of sick seals and abandoned seal pups.
Overall the food on the island is delicious, especially the seafood, and a stop to the women's cooperative at the edge of Patitiri is recommended for those who want home-baked cheese or spinach pies, plus some local almond sweets.
Beyond what you can see or taste there are little secrets around the island, numerous hiking paths to explore, unique fauna and flora, a few interesting landmarks and remains of ancient civilizations. At Agios Petros there is a sunken Byzantine ship dating from around 1200 AD, while remnants of a submerged ancient city can be found at the waters off the rock mass called Psathoura. An old yet strong lighthouse there is considered a landmark in Aegean waters.
Another uninhabited island called Gioura and in antiquity known as Gerontia is home to the important Cave of the Cyclops where many important artifacts from ancient times have been found. There's also the island of Kyra Panagia (or Pelagos), known in ancient times as Euthyra or Efthyros, but named today after the monastery that was built on the eastern side of the island by monks from Mount Athos during Byzantine times. All these small islands are part of the Marine Park and will offer quiet, untouched beauty and rare excursions into a side of Greece that not many know.