In the early morning light, Seaside Park looks less beachfront, more colour-supplement photo-shoot: modish ribbons of green pine and palm, dark wooden promenade, grey pebble beach and pearly blue sea run in stylish symmetry for 5km along the coast. But look more closely, and you'll spot rascally middle-aged men in among those neatly clipped trees, some doing energetic pull-ups from the branches as others slap their fat, bare bellies with loud, self-mocking guffaws. And out on that immaculate dove-grey shingle, a bicycle is wedged haphazardly: its owner is busy mussing up the calm waters with a trail of sploshy ripples.

Incongruity abounds at the Georgian seaside town of Batumi. Set on the sub-tropical eastern coast of the Black Sea, in the shadow of the lush Caucasus Mountains, Batumi has long been Georgia's popular, though increasingly shabby, summer capital. But Batumi has undergone a four-year, radical £350m facelift aimed at turning it into a hip resort. It now boasts a lovingly restored historic old town, and the attractive Seaside Park has striking public art and cafes, upscale hotels and a host of chic nightclubs and restaurants, and the inevitable ferris wheel (surely by now the avocado suite of the tourism-architecture world?).

"I drive around and think ... this road wasn't here a few days ago," says Omer Subasi. In a relentless construction programme, 80% of the town's roads were rebuilt. Omer is general manager of the Sheraton, Batumi's first five-star hotel, which opened in summer 2010, an audacious recreation of the fabled lighthouse at Alexandria (the Radisson, opened last summer, resembles an artfully crumpled, glass cereal packet).

So how is the revamp going down? "The old town, the park – beautiful," says US tourist Penny Lefalas, charmed both by Batumi's history and its modern amenities (five years ago, power and running water were sporadic at best).

Her friend, Delia Rush is less sure about the rash of casinos and hotels. "If there's any more chrome and glass, it risks turning into Vegas," she says. But as head of tourism Irakli Baramidze later explains, this is the first time since Georgia was freed from Russian forces in the 1990s, and the Rose Revolution brought Mikheil Saakashvili to power in 2004, that Batumi has been free to develop. "Investment creates jobs," Baramidze says simply, "and western investment brings us independence and freedom."

Batumi's wealth is the stuff of legends: back when it was known as Colchis, Jason and his Argonauts supposedly sailed here to steal the golden fleece. The vast Roman fortress at Gonio (15km out of town, close to the Turkish border), ornate Gothic cathedral and Ottoman mosque also stand in testament to a rich history. But it was oil that really put Batumi on the map. In the early 1900s, the Rothschild and Nobel brothers were among those who made fortunes exporting oil from Batumi's harbours. And it was relentless innovation that made all this possible – as the fascinating Nobel Technological Museum (georgianmuseums.ge) explains.

But, like the men exercising on the chic waterfront, innovation can jar. In the cobbled fin-de-siècle old town, men play chess at makeshift tables in the shadow of walnut trees, pretty houses with grapevine-entwined balconies frame the view. But at the end of the street, a futuristic casino overlooks a huge fountain featuring Neptune and a group of fembot mermaids, water spurting from their porn-star breasts.

Drive out of Batumi, and nature takes over. In the rolling countryside of Mtsvane Kontskhi (Green Cape), 9km north, sits one of the biggest botanical gardens in the world (tourismadjara.ge): a stirring landscape of misty valleys and gentle lakes, featuring spectacular flora and fauna from nine of the world's key eco-systems. And beyond the gardens, Mtirala national park (mtiralapa.gen/en) rises up: a rich 16,000-hectare wilderness of dense forest and breathtaking ravines on the Kobuleti-Chakvi Ridge of the Smaller Caucasus Mountains. The mountains reach 1,761m above sea-level, trapping the clouds, and making this the wettest, greenest place in Georgia. The drive up the steep winding road into the park is breathtaking: orchards of apple, mandarin, peach and lemon give way to thick forests of fir, maple and eucalyptus. Ravines pierced by waterfalls plunge into deep valleys through which the Chakvistavi and Korolistskali rivers roar. My driver stops to savour the view: "The mountain air, so clean and fresh," he murmurs appreciatively, taking a deep draw on his cigarette.

The hope is that tourism will generate revenue and protect this region. At the Chakvistavi visitor centre – a small hostel and campsite on a picturesque grassy plateau, with a family-run restaurant (+99 593 967 495) – we're met by Ruslan Kontselidze. Ruslan grew up in Mtirala, a place where the tiny villages are named after the families who have lived there for centuries. In 2006, when the park received protected status – partially because the Russian-induced oil and gas shortages were driving locals to use trees for fuel – Ruslan became a ranger, using his local knowledge to help create a network of trails. It's a work in progress. Hiking up the valley's muddy flanks, we step over carpets of fresh walnuts and fat mushrooms; clouds of butterflies drift like bubbles through canopies of hornbeam and beech. As we reach a fast-flowing, bridgeless stream, I come to an abrupt halt, uncertain where to cross. But Ruslan takes my hand, leading me across stone by stone, with the firm dexterity of a tango master. "This is all new for us – we are still learning what tourists want," says my sparky young guide, Tanya. "Most tourists have heard of the war, but know nothing of our country."

Three sweaty hours later, the trail loops us back to the visitor centre, where wooden tables overlooking the stream are set for lunch. Georgian meals are the ultimate crash course in the country's culture, capturing the national sense of poetry, generosity, deep love of country ... and food. An endless array of local dishes arrives. None is fancy, but all are delicious: fat trout fresh from the stream, grilled in vine leaves; hot cornbread with slabs of local butter and cheese; grilled meats with a tangy bean stew. And the ubiquitous khachapuri, the national speciality of baked dough filled with a pool of molten cheese – sometimes raw egg and butter too. I was too stuffed for Turkish coffee and the desert of raw walnuts soaked in honey, but knew it would be rude to refuse.

And all this was just the build up to the main event ... the toast. Toasting is a noble tradition in Georgia: a courtly ritual of elaborate, often poignant tributes to everyone from lost loved ones to Mother Georgia herself. Usually these toasts are made with Georgian wine (really, really good), but today our hosts broke out the chacha: local brandy. I joined in, but at each toast only touched the brandy to my lips. My driver noticed and was having none of it: "You should drink!" he exclaimed. "We drink to Georgia and her great beauty." Now that was a toast worth making.

• Regent Holidays (0845 277 3317, regent-holidays.co.uk) provided the trip. It offers a 12-day Tbilisi-Batumi holiday from £1,115pp based on two sharing, with four nights in Tbilisi and seven in Batumi, in three-star hotels, including breakfast, return flights and transfers. Upgrade to the five-star Sheraton in Batumi for a supplement of £210pp