Guided hikes along Tasmania's unspoiled beaches lead to two of Australia's most remarkable eco-lodges.

There are beaches in the Australian state of Tasmania so empty and untouched that it's almost eerie to stand on them. Not one plastic bottle or bit of old blue rope on the shore. No buzz of airplanes, no pylons in the distance. No sign at all that Homo sapiens ever got up onto his hind legs.

Tasmania may be one of the last unspoiled places on earth. An island that looks like a tiny comma hanging off the south coast of the mainland, it's perhaps most famous for the somewhat inappropriately named Tasmanian devil, a harmless marsupial with a pug-ugly face. But the wildlife, which includes many species unique to Tasmania (a result of the island's isolation), is in danger; the virgin forests, many stands of trees hundreds of years old, are slowly being chipped away by loggers. Eco-tourism may be Tasmania's last, best hope.

Leading the eco-tourism movement are several wilderness lodges, including the new Bay of Fires and Friendly Beaches, that cater to high-end adventure travelers while staying true to strict conservationist standards. Guests spend several days hiking to get to the lodges, led by local guides—that is part of the wilderness experience. But staying in the lodges is far from roughing it. Bay of Fires is a modernist dream, built of wood and glass; Friendly Beaches is the kind of log cabin a Rockefeller might feel at home in. Both places offer wonderful dining. Tasmania is famed throughout Australia for its wines (most notably cool-climate varietals like Pinot Noir and Riesling), produce (especially apples and berries), cheeses (my favorite is the Gruyère from the Heidi creamery) and seafood (renowned Sydney chef Tetsuya Wakuda gets ocean trout from a Tasmanian farm), and all these specialties are in evidence at the lodges' meals. Ingredients are delivered every few days to a point where the nearest four-wheel-drive-only road peters out, then hauled up the hill by the tireless guides, who double as cooks.

Most travelers opt to visit just one of these lodges, but my mission was to check out both. After a day touring the wineries near Launceston, I set my sights on Bay of Fires, located in Mount William National Park on the northeastern shore of the island. The two-day hike there is mainly along white-sand beaches divided by outcrops of red rock, which you scramble over to get to the next long curved stretch. My guide, Amy Frankcombe, a Tasmanian native, was perfectly suited to her job as emissary: She had recently graduated from hospitality school and was an expert on the local wildlife. Following Frankcombe's example, I took my boots off at the start of the first beach and splashed along at the edge of the ocean, although the power of the surf kept me from having a full-fledged swim. The water temperature was a reminder that the next stop south is the Antarctic.

As I watched delicate plovers scuttling around the dunes, spreading their wings like tiny ballerinas raising their arms, Frankcombe educated me about the birds' nesting behavior. She pointed out aboriginal "middens," the piles of crustacean shells left behind by the island's indigenous people. She taught me how to spot wombat tracks.

The hiking was taxing, but not grueling, especially since no one had to carry a sleeping bag; the first night was spent at a standing camp. (Although showers are discouraged—fresh water is scarce—the campsite has beds.) The guides shouldered the food and the cooking gear.

After the second full day of hiking, the group finally reached the lodge. I had a hard time believing it was there, hidden as it was in the bush. The landscape looked so deserted I wouldn't have been surprised if a yeti had crested a nearby sand dune. But as we got closer to the top of a hill I finally saw Bay of Fires, barely revealed on the promontory ahead.

Bay of Fires is the latest eco-centric, hike-and-hide project by Sydney-based architect Ken Latona, who has won awards for work that equally considers environmental and aesthetic viewpoints. The lodge, perched on the edge of a hilltop between two long beaches, seems to thrust out to the sea. At the same time, Latona designed the building with such eco-consciousness that, were it to be removed, there would be no evidence it ever existed because so little damage was done to the land when it was built. The place is completely self-sufficient, using electricity from solar power and filtered rain water for cooking and drinking.

After so much walking, it was a relief to arrive to a tea of homemade brownies and Anzac biscuits (cookies created for the Australia and New Zealand Army Corps during World War I). And it was good leaf tea, in a pot, with a jug of fresh milk. Showering, on the other hand, wasn't so sybaritic. I was surprised to find that I had to hand-pump my own water, but Latona later explained to me that he wanted guests to know the value of every drop.

Feeling clean and fresh from one of life's shorter showers, I whiled away a couple of hours relaxing in the Zen-like calm of the library, which is shaped like a cube, with two walls made entirely of glass that overlook the crashing surf. Then it was time for dinner.

Before I even sat down at the communal table, I was hungrily anticipating the basil-and-arugula gnocchi that I had seen Frankcombe making right before dinner. To go with it, there was a good range of Pipers Brook wines, some of which I had tasted on my tour through Tasmania's wine country, and the excellent local brew, Boag's. Then came steaks of a local white fish called trevally, cooked with chiles, followed by a tangy lemon tart. Certainly not "chef" food, but the guides had a deft, light touch that let the ingredients shine.

The company at the lodge added to the experience. Communal dining tables are an Australian institution—many of Sydney's better cafes have them—and sociable conversation among the 11 of us at dinner, including the guides, soon turned boisterous, thanks to a group of rowdy Australian policewomen who had arrived at the lodge just before I had. After dinner, everyone danced, even though some of us had known each other for only a few hours.

We all stayed up too late; fortunately, breakfast was not painfully early. I had just enough time to have ricotta hotcakes and local smoked salmon before going on a morning kayaking trip. It was pouring rain outside, but the upper reaches of Ansons River were so beautiful—thick with towering gum trees, the peace shattered only by the raucous calls of kookaburras—that it hardly mattered.

I was sad to leave Bay of Fires the next day, but I had plans to visit Friendly Beaches, 80 miles down the coast. Travelers can only stay at Friendly Beaches after completing the rigorous four-day Freycinet Experience. It starts with a boat trip, during which guests catch their own dinner, followed by three days of hiking and two nights at standing camps. Who would choose such a vacation? Well, a bunch of Australian Supreme Court judges were due to arrive at Friendly Beaches the day after I did, and literary events have also taken place there.

The Friendly Beaches lodge lies hidden behind the dunes on its namesake shore, a graceful seven-mile sheltering curve with water so crystalline that a bracing dip in it felt like a healing experience. The lodge was also designed by Ken Latona and is furnished with great character: The dining table is surrounded by 18 different funky old chairs, and mirrors are framed with pieces of driftwood. There's plenty of pampering to be had, from the inviting sofa in the library to the deep baths in the separate sleeping lodges, where generous jars of bath salts are placed next to the tubs to soothe hike-weary limbs.

After a dinner of oysters plucked a few hours earlier from rocks in a nearby cove and chicken kebabs skewered on lemongrass spears, I settled into one of the best nights' sleep I have ever had. The next day seemed far too soon to leave, but one night is all that Friendly Beaches will allow. The philosophy is that it's best to make people go while they're still wanting more. I certainly wanted more. And I'm getting in shape right now so I can earn my next night there.