Bandar Seri Begawan is moving from the water to the land, and it can be measured.

01 Twenty-five thousand hearths in 1521

In 1521 Magellan's expedition called here and its chronicler, Antonio Pigafetta, left a description still quoted five centuries later: a city built entirely in salt water, with twenty-five thousand hearths and the houses all made of wood. It is the first European account of the place, and even then it described exactly what you see today.

That settlement, Kampong Ayer, was the port and capital of the Brunei sultanate for centuries. The city on land is much later: the present capital was called Brunei Town until 4 October 1970, when it was renamed Bandar Seri Begawan. That is, the modern capital's name is half a century old and the settlement that gave rise to it is at least five.

02 A city with everything over the water

It is worth grasping that this is not a picturesque neighbourhood of houses over a river: it is a complete city, with everything that implies, mounted on stilts across some ten square kilometres. Administratively it is divided into six districts grouping almost forty villages, each with its own name and identity.

And it has the whole infrastructure. Schools, a clinic, a fire station, shops and power lines, all on timber and concrete platforms connected by kilometres of walkways. Running water arrives through pipes laid in plain sight alongside the walkway railing, and that image — a pipe following a plank corridor over the sea — sums up how the place works better than anything else.

Transport is its own too. There are no buses and no road taxis: there are water taxis, long narrow boats with outboard motors crossing the river continuously between the bank and the villages. They have no fixed stop and no timetable; you raise a hand at a jetty and agree the fare before getting in.

03 The figures of the move

Here is the part that turns a postcard into a story. Kampong Ayer's population was around 28,000 in 1981. By 2011 it stood at about 13,000. In the 2016 census it was 10,250 across the six districts. That is, in thirty-five years the settlement lost more than half its people.

The reasons are practical and fairly universal. On land there is a road, a car and a garage; there are bigger plots and new housing; there are connections that do not depend on a boat. Living on stilts means keeping timber in permanent contact with salt water, and that maintenance is constant, expensive and hard to delegate.

04 What is lost by moving

What is lost is not just a type of house: it is a type of neighbourliness. In a city of walkways everyone passes everyone else's door, no car insulates you from the journey and distance is measured in minutes on foot or one hop by boat. That way of living cannot be reproduced in a land development, however good the development.

And a building knowledge is lost. Putting up and maintaining a house on stilts in salt water, with tides, permanent damp and fire risk in a timber structure, is a trade learned by doing it. When the number of houses halves, the number of people who know how to do it halves with them.

05 What Bandar Seri Begawan leaves you with

It is a small capital — about 72,000 people in the municipality, a little over 318,000 in the metropolitan area, across 100 square kilometres — and you do not visit it for an accumulation of monuments. You visit it for one thing that exists nowhere else: crossing the river in five minutes and landing in the city's historic centre, which happens to be floating.

What it leaves is the strange sense of watching a move in progress. Not a frozen place nor a lost one, but one halfway across, with both versions of the city in view a hundred metres apart. Which of the two wins is already known. What is still undecided is how much of the first survives inside the second.