It's been four years since I was last in Aceh covering the aftermath of the tsunami and I was braced for the worst on this trip.

A tsunami drill is carried out in Banda Aceh, with droning alarms and people fleeing an imaginary wave.

I had cynically assumed that there would still be huge swathes of wasteland towards the edge of the city.

But those "fields of shards," as one expat memorably described them to me in the dark days after the tsunami, are now gone. In fact, you have to look quite hard to find any trace of the catastrophe that consumed this corner of Indonesia the day after Christmas 2004.

Houses and shops have sprung up where once there was nothing but rubble, bodies and misery. But what is even more encouraging is that the people here are now much, much better prepared for another tidal wave.

This morning we watched as a full scale tsunami drill was carried out, complete with droning alarms and people covered in fake blood fleeing an imaginary wave.

It was well organized and seemed to show that if Aceh was hit again, there would be a chance for some people to escape.

For some, it brought back chilling memories of that terrible morning on December 26, 2004.

Yudi Rinaldi said the drill brought back images of the day he ran for his life as the tsunami surged towards him.

Yudi Rinaldi, 36, and his four-year-old son Ryan, were among those taking part in the Ulee Lee area of Banda Aceh. He told me the drill was traumatic for him - bringing back vivid images of the day he ran for his life as a monstrous black wave of rubble surged towards him.

Then, there were no tsunami shelters for people like Yudi to run towards.

Now, there are several of these specially-constructed buildings around the city, with room for hundreds of residents. There is a system of buoys out at sea linked to satellites, which should give plenty of warning of an impending tsunami.

I only hope the system will never have to be used for real.