Within an hour's distance from Marmari there are many interesting excursion destinations
The fantastic beaches on the Aegean side of Evia, e.g. Beach Giannitsi, Ag. Dimitriou and Kallanios. Check them out !
Dragon Houses on Ochi mountain and around Styra. https://en.wikipedia.org/wiki/Dragon_houses
The ancient marble quarries outside Marmari
Historic winery MONTOFOLI in Karystos. http://www.montofoliwines.com/site/
The cooling greenery waterfall outside Platanistos and the fantastic Potami beach.
Visit the medieval Castello Rosso above KarystosÂ
Boat trips to completely private beaches on the Petalioi Islands https://www.mysteriousgreece.com/travel-guides/islands/euboea/petalioi/. Some of the islands are private but there is public beach access so you always have the right to use the beaches to swim.
In addition, it is very easy to take the morning ferry for a day trip to Athens. Buses are waiting at the ferry stop in Rafina that go directly to Athens city center, reverse in the afternoon/evening for return. Or maybe all night at Bouzouki in Athens and back with the first morning ferry.
At Alexandris in Karystos, you can rent a car or scooter for private excursions, otherwise we organize minibuses for group excursions. To fully explore the fantastic and completely untouched Aegean side of Evia, you need a four-wheel drive jeep, which can also be rented from Alexandris http://www.joyriderental.gr/