God created the Greek islands last -- or so the story goes -- an afterthought of sorts.

When the Earth was pretty much finished, according to the legend, a handful of rocks remained. Not knowing what to do with them, God tossed the stones over his shoulder into the Aegean Sea. And, thus, the Greek isles were born.

Today, more than 1,000 of these "rocks" are scattered throughout the Aegean, from Crete in the south, largest of the islands, to the northernmost isle of Tha'sos. For most people, a trip to Greece would not be complete without a visit to at least one of these Aegean gems, with their charming whitewashed villages and their long stretches of sandy beaches along cool aquamarine waters.

While the spectacular scenery often proves to be the primary draw, most people do not realize how vastly different the terrain can be from one group of islands to another. The Cyclades, for example -- a cluster of picturesque islands in the central Aegean -- are rocky and barren, while the Sporades, in the north, are surprisingly verdant.

Two of the best-known islands in these groups, Santorini (also known as Thi'ra), a crescent-shaped isle with volcanic origins located at the southernmost tip of the Cyclades, and Ski'athos, the most cosmopolitan island of the Sporades, are both jewels in their own right. But they have little in common. . However, a glimpse, even a brief one, at both of these magnificent islands can give a first-time visitor a clear idea of how diverse the Greek islands really are.

Sitting on a terrace on Santorini overlooking the deep blue Aegean, you cannot help but feel that you are in a place that is virtually indescribable. "The reality is so astonishing that prose and poetry, however winged, will forever be forced to limp behind," author Lawrence Durrell wrote of Santorini in "The Greek Islands."

Stretched before you is a breathtaking panorama: an expansive semicircular bay framed by dark, precipitous volcanic cliffs that plunge abruptly into the sparkling blue sea 900 feet below. Perched along the edge of this perilous l8-mile rim lie isolated whitewashed villages, their odd cylindrical-shaped houses creating the impression that they sprouted from the dusty earth itself. From a distance, the stark rocks topped by gleaming villages look like snow-capped mountains.

In the center of this dramatic bay is the bustling capital of Thi'ra, a cosmopolitan town with terraced levels of shops and restaurants. The town overlooks a volcano that still occasionally smolders and an ominous mass of black lava. More than 3,000 years ago, the volcano erupted so violently that most of this once circular island sank into the sea, leaving the ragged cliffs and the sea-filled caldera behind.

At some points in history, scholars have postulated that this may have been the site of the legendary city of Atlantis. There is more reason, however, to connect Santorini with the Minoans. Greek archeologist Spiros Marinatos even theorized that the powerful tidal wave that followed the cataclysmic explosion on Santorini may have been responsible for the collapse of the Minoan civilization on the island of Crete, about 70 miles away.

In 1967, while researching the ancient eruption, Marinatos began excavations on the southern coast of Santorini at Akrotiri. Under layers of volcanic ash and pumice, he uncovered a well-preserved settlement dating back to Minoan times. The city is almost intact, complete with irrigation canals, streets and houses. There also were colorful frescos, which have been removed and are now housed at the National Museum in Athens. Excavations are still in progress, but the rest of the site is open to visitors.

Undoubtedly triggered by the volcano's legacy, a sense of impending disaster may confront the visitor here. But it is an intriguing uneasiness. Indeed, a hair-raising donkey ride up the winding road dug into the red and black volcanic cliffs is a must on every adventure-loving tourist's itinerary.

Yet, the sinister scenery with its raw, forbidding cliffs can also be oddly seductive. The blue sea below is calm, the gentle breeze soothing and the whitewashed houses -- connected to one another in an intricate scheme of stairs and terraces -- endearing. At night, the moonlight dances on the water, a shimmering silver streak in the darkness; the enchanted silence is interrupted only by a passing scooter or a confused rooster.

One of the most serene spots -- from an admittedly biased viewpoint -- is Oi'a, a small, quiet village located on the northern tip of the island about 10 miles from Thi'ra.

Oi'a's whitewashed houses, many of them partially built into the ashen cliffs, line the rim of this isolated village. Once the wealthy capital of Santorini, Oi'a was almost completely destroyed by a severe earthquake in 1956. Ghostly ruins remain -- empty, eerie caves dug into the pumice cliffs. But above these remnants of the past, new brightly painted homes have been built. Slowly, this small village of 500 (down from the 3,000 who lived there at the time the quake struck) is once again becoming a popular haven for tourists.

Accommodations for visitors range from simply furnished rooms in hotels, like the Lauda in the heart of the village ($13.80 double, without meals), to fully equipped guest houses on the outskirts of town operated by the National Tourist Organization.

One of the most charming settlements of guest houses is Perivola, a tiny bit of Aegean paradise run by a gracious mother-and-son team, Nadia and Costis Psihas. A small blue gate, a picket fence of sorts and wide steps lead down to five separate houses. Each house has a kitchenette, a private bath and a terrace with a panoramic view of the caldera. Perivola is truly a labor of love, painstakingly decorated with clay pots, fresh flowers and colorful blankets and rugs, handwoven by Nadia herself. And all of this for a reasonable $17 a person per night, without meals.

While Oi'a may be peaceful, it is definitely not a place for the lazy. Getting anywhere requires walking up and down one series of steep steps after another. But each winding turn reveals new delights: windmills, colorful flower pots, bleached white churches with bright blue domes.sw sk

Going for a swim is no easy task either. From the village, 246 steps zigzag down to a small beach called Ammoudi, which literally means sand. Actually the beach is made up of small red pebbles. As beachgoers soak in the sun's rays and splash in the turquoise sea, weather-worn men mend their fishing nets and paint their dry-docked caiques. A trip down to this attractive beach is well worth it, but one word of advice -- take a mule back up.

The flip side of the island, however, provides an easier route to the sea. Here, the landscape slopes gently. A paved road carves its way through fields of small sweet tomatoes and bittersweet grapes. Donkeys, goats and sunflowers dot the sweeping, but dry, countryside. Here, the beaches are of fine black sand. The most popular bathing spots, Kamari and Perissa, are both easily accessible by bus from Thi'ra.

As the sun sets over this isle, its bewitching harshness and captivating serenity come together in an explosion of color. In Oi'a, as the red sun begins to hover over the horizon, head for a crumbling, romantic fortress at the edge of town. Ribbons of color -- red, yellow, green, purple, orange -- fill the sky. The expansive blue sea below, reflecting this kaleidoscope, changes too, taking on a pink, violet hue. Inside darkened silhouettes of houses and taverns, lights twinkle warm invitations to a satisfying meal and a glass of retsina, a spicy homemade wine. In the distance, the moon rises over the glittering lights of Thi'ra.

Unlike Santorini, sundrenched Ski'athos in the northern Aegean is mostly a gentle place, where forests of pine trees and long stretches of golden sand as fine as flour line calm bays of crystalline water. Gone is the stark drama of Santorini; here only tranquility reigns.

Plunge into the cool, refreshing water that is as still and clear as a swimming pool's. Take a deep breath, filling your lungs with the fresh scent of pine. Gone are the pebbles of the Cycladic shores, beneath your bare toes is soft sand shimmering in the sunshine.

Few places in Greece can boast such a beguiling combination of sea and pines, but the mile-long beach of Koukounaries is certainly one of them. Many consider this beach, named after the pine cones scattered on its shore, the most beautiful in the country. Row after row of pine trees separate a fresh-water lake from the silky golden sand and the aquamarine sea. An ultramodern deluxe hotel, the Ski'athos Palace, and the excellent Xenia grace opposite ends of this Mediterranean wonderland, giving it a cosmopolitan look.sw sk

Gnarled olive trees, pines, honeysuckle, thyme and wildflowers cover acre after acre of rolling hills. Everything is fresh, fragrant and green. Vegetation, scarce on Santorini, is plentiful here. Just off shore, small verdant islands surround Ski'athos and the purple mountains of Pelion on the mainland are etched in the distant haze.

You will find numerous villas, cottages and hotels along the eight-mile route that hugs the craggy coastline from Koukounaries to the main village, also called Ski'athos, where most of the island's 4,000 residents live. The houses in this town of winding narrow streets are painted typically white. But they are different from the houses of the Cyclades. These have red tile roofs and wooden balconies rather than whitewashed terraces.

A picturesque harbor with colorful caiques, elegant yachts and several cafe's and overpriced restaurants serves as the town's center. On one end of this cluttered cove, fishermen unload their daily catches under wide-leafed plane trees. At the other end, villagers and visitors alike casually stroll through the park on the Bourtzi, a small pine-covered islet, which was once home to a medieval castle.

Small boats leave this graphic harbor every morning around 10 for a day trip around the island. Like two-faced Santorini, gentle Ski'athos also has a rugged side. The northern coast of this island is storm-lashed. Bare rocks tumble to the water's edge, and the beaches are full of flat, white stones.

But this side of the island has its gems as well. Lalaria, a beach named after the white pebbles on its shores, is one of them. But the special feature here is a ragged rock at the end of the beach, which has a huge hole in it. Part of this wind-carved crag is underwater, so you can actually swim through the hole. The water is pristine, so clear you can see the bottom 10 feet below.sw sk

Another stop on the boat trip is the old town of Ski'athos, known as Kastro (fortress), built on the top of these rocky cliffs to protect against pirates. Most of the town is in ruins today, but a tiny church with relatively well-preserved 17th-century frescoes remains intact.

By evening when the fleet of tiny caiques have long since returned, the town's sleepy harbor awakens with activity. The sky turns a gentle pink and dozens of swallows dart through the air. In what has become a daily summer ritual, people saunter slowly along the waterfront, most of them dressed in their Sunday best.

Get a table near the water and enjoy the parade. Share a carafe of ouzo, a licorice-flavored aperitif, with a friend, and munch on a plateful of fresh octopus or savory cheese pies. Or have a cup of thick, bitter Greek coffee. If you are still hungry, venture into one of the town's many taverns, perhaps one overlooking the bustling harbor. The specialty: grilled fish, fresh from the Aegean, of course.

After dinner, join the fun back at the waterfront. Sit at the cafe' called Neos Kosmos if you have a sweet tooth and order a bowlful of mouthwatering loukoumades, fried dough rolled in balls and drenched with honey and cinnamon.

The night is not over yet, if you do not want it to be. You can dance till dawn at a disco or listen to bouzouki music at a nightclub. Or you can always take a quiet stroll in the moonlight.

Such is the diversity of the Greek islands, God's Aegean afterthought.