My driver drops down a gear to kick-start our car. There's nothing wrong with it; it's just a ritual we have to go through to negotiate the steep roads of Saint Lucia. This Caribbean island may be only 27 miles long by 14 miles wide, but its mountainous terrain (reaching its peak at Mount Gimie at 3,120ft) threw down the gauntlet to the road-builders, who cut as best they could into its volcanic mass. The result is a corkscrew of highways that will take you where you want to go – eventually.
That's OK. I'm in no hurry and anyhow I'm distracted at each switchback by the dense jungle, steaming in the humidity. Occasionally, we emerge in a community of squat multicoloured houses with corrugated iron roofs, where balustraded porches provide a shady place for homeowners to escape the burning sun. Then it's back into the foliage, the ocean flashing a blue smile between the trees.
Saint Lucia has sugar-fine sands worthy of lounging on for your whole stay, golden in the northern holiday playgrounds of Gros Islet, and Rodney and Marigot bays, and silvery in the south around the iconic volcanic spires, the Pitons, where the island's top-end hotels cluster. But the interior is equally magnetic – a tangle of tropical forest filled with possibilities for active fun, from hiking to the island's tropical heart on the Edmund Rainforest Trail, to ziplining at the Treetop Adventure, and slathering your body with restorative mud at the Sulphur Springs Park.
There are cultural diversions, too. The spring Jazz Festival and summer Carnival and poetry lovers can take a turn around Derek Walcott Square, one of the few places of architectural note in the capital Castries, which honours the poet and Nobel Laureate who set his epic poem Omeros around Gros Islet. The island's history is neatly told at Pigeon Island, and, for a taste of life today, communities such as the fishing town of Soufričre, the old French capital, come alive during market hours. Pretty Anse La Raye is the place to spend Friday night for the Fish Fry.
For a radical alternative to lying on the beach, visit Saint Lucia's newest attraction, Our Planet, which opened in Castries in June. The multimillion-pound centre, a partnership with Noaa and Nasa, invites visitors to explore Saint Lucia specifically and Earth in general to gain a greater understanding of the man-made and natural challenges facing our environment. As well as sampling views of our planet from space, visitors can play games where they create hurricanes and power cities, and feel the effects of extreme weather in a special-effects theatre. All profits from ticket sales are used to fund environmental projects on the island.
Tourism has been one of the main sources of income for Saint Lucia for 30 years, but now the island is going upmarket, hoping to poach high-rolling holidaymakers from Barbados and beyond to the luxury hotels that have popped up during the past decade, notably Jade Mountain, Boucan and the transformed Jalousie Plantation, this month reborn as Sugar Beach, a Viceroy Hotel.