In a far-off corner of Indonesia is a hot, dusty island half frozen in time. Its towering grass-roofed houses and rare birds, beautiful horses and deadly staged battles, along with its ancient animist religion, make a visit to Sumba seem like a step back into the distant past.

But change is coming to this mystical isle. It may appear isolated, in Indonesia's remote southern Nusa Tenggara chain, but Sumba is close to Australia and plans are afoot for Bali-style development.

In Prai Yawang, a village in Rindi district, a group of elderly men sit in the shade, smoking and chewing sirih pinang (betel nut). In the village yard stands a tall, pointed, grass-roofed uma ndiawa, or house of the spirits. This is the type of architecture that visitors most associate with Sumba and, once, special objects would have been stored by shamans in the roof (it's possible some relics are still there; only shamans are allowed to enter). There is an area in front of the uma ndiawa, known as the katoda, where ordinary people are allowed to offer up prayers to their ancestors.

The men - among them Kuapa Rihi, who wears a turban and says quietly that he thinks he is about 70 - are here for a ceremony that no one will explain but which is expected to last for hours, possibly all night. The mysterious ritual has its roots in Marapu - a form of ancestor worship that about 10 per cent of islanders still practise. Some of the men speak only Bahasa Sumba, the native language of the island. A few of them are respected shamans who, they claim, are able to read the future.

Officially, most of the islanders are now Christian; Indonesians must register as belonging to one of five recognised faiths, and Marapu, which means "that which is not seen", is not among them. There is considerable pressure to convert and, in the process, older people fear that Sumba's unique traditions are being lost.

Muttu Pattimay, who is about 80, says he does not want to lose touch with the ancestors.

"We are living here because of them. They are the ones who brought sirih pinang. Without them we would not be here," he says, before being rudely reminded of the outside world.

A large gleaming car pulls up and out jump a group of Chinese tourists. Without asking permission, they begin snapping photographs of the old men. When the tourists have had enough, they disappear just as quickly as they arrived.

Well-managed tourism could, however, prove beneficial to Sumba. The island is already popular with birdwatchers, who come from across the globe to see the several rare species that can be found here. So, given its unique traditions, it's fair to assume that many more visitors would come if the island were easier to reach.

Each part of the island still has a traditional "king", say the men of Prai Yawang, and many of the royals wield considerable clout. In Ngonggi, in the southeast, the burial of the local king is due to take place this year and is expected to attract visitors from across the island.

Once, when a king died, his remains could have been stored for years, until there was little left except bones, as shamans deliberated on the "right time" for a lavish funeral. The tombs of past kings, many of which sit beneath stone slabs supported on pillars, are some of Sumba's most impressive sights.

Traditionally, the island has had a caste system, with nobility, slaves and those in between. At one time, a king's slaves would have been expected to follow him to the grave, to serve him in the afterlife. If a woman moved communities to marry a king, she would take with her a slave, who would marry a local man, thus ensuring the new queen had someone from home to keep her company.

Officially, these ranks no longer exist. In reality, they are still very much a part of daily life.

King Umbu Ndjurumanna lives in Prailiu, on the outskirts of the main city, Waingapu. He is a friendly man and works in an administrative job in the government. In a sign of the times, his wife is Australian and they hope to make Prailiu a tourist attraction. Although he is officially no more than an ordinary citizen, he is treated with deference by his entire community, for whom there is no doubt he is of royal blood.

"If we are dealing with adat [traditional law], our status [as kings] is clear," says Umbu. "That is a matter of adat, not a matter of government."

In 2007, following his lead, the king's entire community converted to Christianity. Nevertheless, says Umbu, there is some tolerance of the old ways: "There are Christian priests who understand. There are those who do not want to understand at all."

When the village converted, the relics stored in the roof of its house of the spirits, which some Christian priests regard as demonic, were thrown out. Some may have been hundreds of years old but they were left under a tree and were, over time, taken away by passers-by.

In Sumba, reminders of the past - spent munitions and wrecks from the second world war as well as the tombs and traditional pointed-roofed houses - are not hard to find. The older people of Prai Yawang fondly remember the Allies who liberated Sumba, along with most of eastern Indonesia, from the Japanese in the later stages of the war.

In Prailiu, the nose of a wartime shell has been turned into a bell to call people to church, and the parishioners are again counting on Christian countries to support them, this time against militants who want to "Islamicise" Indonesia.

And it's people from the likes of "Christian" Australia who may one day fill Sumba's impressive beaches, bringing with them tourist dollars.

Contact with the outside world, however, is a double-edged sword. Many here are aware that isolation has preserved Sumba's traditions.

Only time will tell whether the island becomes the next Bali. In the meantime, Sumba offers a fascinating glimpse into a way of life that is fast disappearing from southern Indonesia.

Staged battles, horse racing a highlight of Sumba, Indonesia

Sumba is known for holding battles that, although staged, can still turn deadly, and Waingapu, the island's largest town, is famous for its annual horse-racing festival.

The battles, known as pasola, take place in February and March in the west of Sumba. Fighters charge at each other on horseback, throwing spears, in a rite intended to ensure a good harvest. Although widely described as "mock" battles, the aim is to draw blood and occasionally that goes a step further. The pasola appears to have originated as a form of human sacrifice.

Horse-racing events take place all over the island at various times of the year, and they frequently turn rowdy. On occasion, they have been cancelled due to violence. The major event in Waingapu usually takes place in October, and boy jockeys, some of whom are still at primary school, train for the games at the town's horse-racing track for weeks in advance.

The small horses, said to be descended from those ridden by Genghis Khan's troops and sometimes known as kuda sandel ("sandalwood horses"; after the sandalwood that was once exported from Sumba), are known throughout Indonesia and beyond.

Getting there: Cathay Pacific, Dragonair and other airlines fly daily from Hong Kong to Bali, from where Wings Air runs a service to Waingapu, in Sumba.