On 26 December 2004 at 07:59 local time, a magnitude 9.1 undersea earthquake struck 240km west of Sumatra, Indonesia, rupturing the greatest fault length of any recorded earthquake (1,500km long), and releasing energy equivalent to 23,000 atomic bombs.

The tsunami waves it triggered spread across the Indian Ocean at speeds of up to 800km/h (as fast as a jet airliner), devastating coastal areas in more than a dozen countries and killing 230,000 people in what would become one of the greatest natural disasters in modern history.

But it was Aceh, Indonesia – a province already blighted by decades of civil war – that was hardest hit, particularly the capital Banda Aceh, where waves of up to 20-30m swept through the city, destroying more than 60% of its buildings and killing an estimated 61,000 people (around 25% of the population.)

Twenty years on, Banda Aceh has been rebuilt and is thriving once more. “The transformation has been extraordinary,” says Sam Clark of UK-based Experience Travel Group, which has recently launched trips to the city. “It’s a testament to the fortitude of the Acehnese people to see how Banda Aceh has risen from the waters.”

Clark goes on to cite the locals, their culture and the moving tsunami memorials as some of the highlights of a visit here, as well as the city’s proximity to other attractions including the coffee-growing Gayo Highlands, the snorkelling and dive sites of Weh Island and the rainforests of Gunung Leuser National Park – one of the last places on Earth where critically endangered orangutans live in the wild. “Banda Aceh and the wider province represent the final frontier of adventure tourism in Indonesia,” he says. “And for the intrepid traveller, they’ll find it’s a place well worth seeking out.”