Shops from French colonial days line a street in Kampot, which was Cambodia’s main port before the rise of Sihanoukville and more than a half-century of decay. (Dustin Roasa/For The Washington Post)

As the sun sank over the tree-lined Kampong Bay River, Kampot, a town on Cambodia’s southern coast, stirred to life. The locals, who’d spent much of the day hiding from the heat in their homes and shaded alleys, emerged into the atmospheric streets, where sun-stained, mustard-colored French colonial shop houses provide the backdrop to the rhythms of daily life.

Old men with fedoras and graying sideburns gathered at a corner cafe to play chess, triumphantly thwacking hand-carved pieces against thick wooden boards. Small groups of boys fished on the banks of the river with homemade bamboo poles, while groups of teenagers with mussed and shaggy haircuts and wearing glittery T-shirts yelled “Hello!” and giggled at strolling tourists, who are a small but growing presence in this largely unexplored corner of Southeast Asia.

My wife and I had come here to escape the grit and bustle of Phnom Penh, where we live, and to show my visiting mother-in-law a slice of authentic provincial life. With crumbling historic architecture, largely unspoiled countryside and specialty regional cuisine, Kampot and Kep, seaside towns separated by a 30-minute car ride, are unlike anyplace else in Cambodia.

Although tourism has taken off in the past decade — for much of the 1980s and ’90s, the area was off limits due to the presence of the Khmer Rouge — the two towns have avoided the dizzying and sometimes tacky growth of places like Siem Reap, where busloads of visitors swarm the ancient Angkor temples, and Sihanoukville, which caters to backpackers looking for a cheap alternative to coastal Thailand.

Instead of mega resorts and budget dives, Kampot and Kep have attracted a smattering of boutique hotels, bars and restaurants that draw on the area’s history as a stylish retreat in the last century, when the French and Khmer elite spent weekends here soaking up the Riviera-like vibe.

Now, a new wave of expats and tourists is discovering the place. Ben O’Reilly, an Irishman who runs Mea Culpa, a guesthouse and wood-fired pizza restaurant set in a shady garden in Kampot, arrived as a tourist in 2004 and never left. “It stole my heart,” he said. “The stunning beauty of the people and the area makes it stand out unlike anywhere else I’ve ever been.”

A large part of the area’s appeal is its time-capsule quality: While much of Southeast Asia has been eager to demolish remnants of the past and modernize, Kampot and Kep have preserved a century of Cambodian history in their streets and surrounding hills. As we rode into Kampot with our taxi driver, a 56-year-old local named Eav, we watched the past flash by through the windows of his Toyota Camry.

There, on the left side of the road just outside town, Eav pointed out a salt plant built by the Khmer Rouge. “They exported salt to the Chinese in exchange for arms,” Eav said. Farther in was the columned and pleasingly dilapidated governor’s mansion, a symbol of colonial power, and its necessary counterpart, the French-built prison, which is still in use. Next came the Chinese school with its elegantly curved roof, a reminder of the sizable influence of the entrenched Chinese-Cambodian community here.

“The people here are proud of these buildings, and we want to keep them,” said Eav. “The local authorities are doing their best to preserve them.” So, too, are the entrepreneurs who have come here, many of whom have restored old villas and shop houses.

One such business is Epic Arts Cafe, a nonprofit that employs people with disabilities, where we had coffee and fresh-baked chocolate chip cookies. After a stroll through the streets surrounding the abandoned market at the center of town, we reserved seats on a boat trip down the Kampong Bay River and into the Gulf of Thailand.

As we puttered along the mangrove-lined river in a long-tail fishing boat with Capt. Chim, a man in his early 30s, we passed villages of wooden shacks with corrugated metal roofs suspended over the water on stilts. Although Kampot is not as cosmopolitan as it once was — it was the country’s primary port until the emergence of Sihanoukville in the 1950s — its access to the ocean continues to draw a mixed crowd.

We passed a fishing village with a white minaret poking out from a clump of palm trees, home to Cham Muslims, an ethnic minority that makes up 5 percent of Cambodia’s population and tends to live apart from the majority Khmer. Several minutes later, on the opposite bank, ethnic Vietnamese fishermen waved to us from moored boats as they prepped their nets for the night’s work ahead.

Gradually, the river widened until it deposited us into the Gulf of Thailand. Capt. Chim stopped the boat at a large sandbar some distance from land. Nearby, a hulking sand-dredging barge, pitched on its side, sat idle, a sign that the area’s small-scale approach to development would not last forever. A joint Cambodian-Vietnamese firm is building a resort and casino here on reclaimed land, Capt. Chim told us.

That night, back on Kampot’s sleepy riverside, we had well-made gin and tonics at the breezy Wunderbar before sampling the area’s famous fresh seafood at open-air and candlelit Rikitikitavi, where the fish amok, a coconut-milk mousse made with white fish, was superb.

The next morning, we were ready to tackle the nearby Elephant Mountains, a series of jungle-covered hills that rise toward the coast before sloping dramatically into the sea. A trip up Bokor Mountain, which can be arranged through travel agencies in Kampot, is one of Cambodia’s essential experiences.

As our car wound its way up the mountain, gaps in the thick roadside foliage revealed breathtakingly clear glimpses of the flat rice plains and salt fields that stretch for miles below. Near the top, tucked away in a small valley, is Bokor Hill Station, which the French built in the 1920s as a retreat from the sweltering Phnom Penh heat. They abandoned the area during fighting with Cambodian nationalists after World War II, and apart from some short-term stays by Khmer Rouge guerrillas, the Catholic cathedral, villas and four-story Bokor Palace Hotel have sat empty.

Rust-colored lichen and green moss have made primitive splatter canvases of the buildings’ gray stone and reinforced concrete exteriors. As I wandered through the empty hotel, the wind whistled down empty corridors, the hand-painted floor tiles covered in layers of dust and grime. On the back veranda, where colonialists would have sipped aperitifs and enjoyed the fresh air, I chatted with a large family of Cambodian tourists from Phnom Penh. “There are ghosts in there,” said a man named Hang, to nervous laughter from his family members. “People lost money at the casino and jumped to their deaths. They haunt these buildings.”

Kep, the seaside retreat 15 miles southeast of Kampot, has its share of ghosts, too. Less a town than a collection of small resorts and seafood shacks, in the post-World War II years it was a glamorous weekend getaway for the Khmer elite, who vacationed in Le Corbusier-inspired villas built by the country’s premier architects.

These villas reportedly hosted wild parties with actors, pop stars and artists who were driving a cultural renaissance in the 1950s and ’60s. Now they’ve been reduced to little more than their foundations and a few walls. You can wander through them and imagine their former grandeur, but the only signs of life are the graffiti scrawled on the walls and the disused clotheslines left by squatters.

One exception is Villa Romonea, a six-room hotel that was designed as a private villa by leading Cambodian architect Lu Ban Hap in the late 1960s. The modernist-style house was the lifelong dream of a local businesswoman who grew up across the road. But she lived in the house for only a few years before the Khmer Rouge took over the area and eventually executed her. Her vision lives on, though, in the house’s exquisite design, with its curved rear facade, which mimics the bend of the shoreline it faces, and the walls of windows that keep the minimalist interior airy, cool and light.

Life in Kep revolves around its rocky beaches, so in the late afternoons, it’s best to head there to watch the locals gather to buy snacks such as the scrumptious num ompong, tubular rice cookies covered in black sesame seeds, from street vendors. The cookies go well with Campari and sodas at the Sailing Club, a nearby sky-blue bar and veranda.

Kep is known for its fresh crab, and the best place to sample it is Kim Ly restaurant, where metal cages containing the day’s catch bob in the gentle surf. Sitting at a table facing the water, which glistened through tiny cracks in the floor below us, we devoured a heaping plate of crab, which is prepared with fresh green peppercorns from local farms. The way the sweetness of the crab meat interacts with the richness of the coconut milk and the spiciness of the peppercorns has made this dish a local institution.

The area’s peppercorn is also renowned. Once a prized ingredient in the world’s best kitchens — particularly in France — the crop was all but destroyed during Cambodia’s 30-year civil war. It has made a comeback in recent years, and in 2010 the European Union and the Cambodian government granted it “geographical indication” status, which has raised its profile.

I wanted to see these farms firsthand, so we rented motorbikes and drove up into the low hills half an hour outside Kep, where peppercorn plantations thrive. Down a rutted dirt road is the Heng Kimean farm, run by 55-year-old Saem, who showed us around the clumps of vines growing on wooden poles spaced several feet apart.

He pulled a fresh sprig from a mature vine and offered it to us. We munched happily, the spice’s mild piquancy tingling in our mouths. “I’m selling more and more to France,” said Saem. “The chefs in Paris have found us again.”

After years of inaccessibility, the world is also once again discovering the charms of Kampot and Kep.

Roasa is a writer based in Phnom Penh.