If mountain activities are your passion, Greece is a hidden paradise! The mainland, and even the largest area of the islands is covered by mountains - most of which are barren, rocky, with low shrub coverage and virtually no water flows of any kind.
For lush vegetation and tree coverage can be found in Epiros, Macedonia, Pelion, and the Peloponnese interior. In these mountains rivers and creeks of all kinds and sizes meander through the pine and oak trees.
Since Greece receives the majority of tourism in the coastal areas, the mountains are virtually unexplored by the masses, so chances are that you will have a lot of comfortable space to yourself if you spend your days hiking.
But this relative isolation comes with the proportional lack of services, maintenance, and proper signposting. With the exception of Samaria gorge in Crete, where the hiking path is well marked and rest areas are sprinkled throughout, you should treat the rest of the hiking path in Greece with extreme caution.
Greek newscasts often host stories of tourists who had to be rescued from dire situations in remote areas, and oftentimes, of tourists who were injured (or worst) hiking, kayaking, climbing, or rafting in the remote wilderness of the land.
It is advised that you seek the advice and services of local guides if you plan to engage is outdoor activities in the mountains of Greece.
By law, free camping is officially not allowed anywhere in Greece, so if you prefer to live close to nature you might want to reserve a plot of land in one of the thousands of official camping sites that can be found everywhere tourists might go.
The reality is that these organized camp sites offer "camping" only in name. In reality they offer an experience diametrically opposed to what most travelers would prefer when choosing this kind of accommodations. That's because the vast majority of camp sites in Greece are packed to the tree brunches with people, tents, and people. We've seen camp grounds that are reputable, comfortable, and organized, but we've also seen some that looked little different than shanty towns.
On the flip side, these organized camping sites are inexpensive and offer a host of basic needs such as communal bathrooms and showers, running water, electricity, and most likely easy access to a beach. If you don't mind the crowds and lack of privacy, booking a couple of square meters of land under a tree that shades another three or four tents might not be a bad idea.
Resourceful travelers who long for the genuine camping experience find remote beaches where they can pitch a tent for some care free and inexpensive living. If that's the route you plan to go, you should know that local police might mar your experience. The Greek laws on free camping which were updated as recently as 2013, prescribe fines of €300 per person (or structure - ie tent, camper, RV, etc) paid as if you were paying a traffic citation, as well as imprisonment up to six months and/or fines up to €3000.
But if you've ever been to Greece, you know that laws notwithstanding, there are tons of places where free campers have taken over with the discreet permission of the local society and shop owners. So chances are good that if you free camp at a beach where tons of other foreign tourists camp, no one will bother you.
There are plenty of things for the active traveler in Greece. Many organized beaches, and beaches near popular tourist destinations offer para-gliding, hand-gliding, water skiing, canoing, jet skiing and many other activities. Many hotels near beaches are also well equipped with gyms, and outdoor exercise facilities, tennis courts, and in rare cases, golf courses.
Many organized and semi-organized beaches have a volleyball net installed and spontaneous games spring up at random, or at scheduled (by local bars) times.