Twelve days after the tsunami hit, Annan and World Bank President James Wolfensohn flew over the island's west coast in a Singaporean helicopter and then drove to the shattered port of the main town of Banda Aceh, where families picked through piles of rubble six feet high. The stench of rotting bodies hung in the air.
"I have never seen such utter destruction mile after mile," a shaken Annan told reporters afterward. "You wonder where are the people? What has happened to them?"
Relief workers are still trying to come to terms with the scale of the Dec. 26 earthquake and killer waves that hit 11 nations. With tens of thousands and still missing and threatened by disease, the United Nations said the number of dead would keep climbing.
"I think we have to be aware that very, very many of the victims have been swept away and many, many will not reappear," U.N. humanitarian chief Jan Egeland said in New York. "The 150,000 dead figure is a very low figure. It will be much bigger."
Hardest hit is Sumatra, which was closest to the 9.0 magnitude quake, where all of Indonesia's some 100,000 death's occurred.
The country increased its toll by 4,289 on Friday, after uncovering thousands of bodies in and around the shattered coastal town of Meulaboh, which was cut off from the rest of Sumatra for days because roads were swept away and sea jetties destroyed.
U.N. and Indonesian officials also said Friday they would not scale back cooperation with the U.S. military on Sumatra despite terror fears raised by the presence of an extremist Islamic group with alleged al Qaeda links.
The Laskar Mujahidin set up a camp in Aceh province and posted a sign that read — in English — "Islamic Law Enforcement." Its members said they have been collecting corpses, distributing food and providing Islamic teaching for refugees.
The presence of the extremist group, accused of involvement in Christian-Muslim fighting elsewhere in Indonesia, has generated fears that U.S. military personnel and others doing relief work could become terror targets. It also underscored the fine line foreigners must tread between being welcomed or viewed as invaders.
Annan's visit came after he attended aon Thursday on how to turn one of history's largest-ever aid packages - nearly $4 billion in pledges - into food for the hungry and shelter for the homeless.
The U.N. chief urged nations to come up immediately with their promised aid, and to break with past practices of pledging much and delivering little.
U.S. Secretary of State Colin Powell meanwhile is in Sri Lanka, where more than 30,000 people died. Powell, who was at the aid conference in Jakarta, arrived in Galle, Sri Lanka, Friday to inspect tsunami-devastated areas in the south and hold talks on relief efforts with the government.
"I had a chance to witness the destruction firsthand and only by seeing it on the ground can you really appreciate what it must have been like on that terrible day. But I am impressed to see people cleaning up, helping their neighbors, starting to clean up shops and homes," Powell said after surveying the damage.
Powell flew into Galle aboard an Indonesian Air Force helicopter, landing at a 17th century fort and near a pile of debris from which bodies were still being pulled this week.
The local bank is now a tsunami aid center; not far away, garbage is rotting in the streets and water lines - cracked open on the sidewalk - are a breeding ground for disease.
Despite all the destruction, at his hilltop residence overlooking the city Kingsley Wickramaratne, Governor of Galle Province, told CBS News that he is optimistic that tourists will return as early as October.
British Foreign Secretary Jack Straw, who visited the Thai resort city Phuket on Friday, indicated that the number of Britons who died could double from his government's earlier estimate and called the effort to identify thousands of bodies one of the biggest international forensic operations in history.
"The scale of the effort still required is truly daunting," said Straw. "It is impossible to tell the country of origin of most of these poor souls without forensic examination."
While some areas remain scenes of total devastation, other Thai resorts are looking to the future. Cleanup on several beaches is almost complete and tour operators are eager to get back to business.
"It's amazing how fast things have gone back to normal. The Thais have done a brilliant job of organizing disaster efforts and getting things cleaned up," said Peter Elsey, 48, an English tourist who lives in Singapore and owns a home in Phuket.
As the international aid effort continues, Australia leads the world's governments with a total aid pledge of $810 million, followed by Germany, Japan and the United States.
Private donations are also pouring in. A telethon in Saudi Arabia raised $67.4 million in 11 hours: with donations ranging from diamonds to tents and blankets. In Norway, four young girls sold their Christmas presents, raising nearly $1,000.
Worldwide, benefit concerts are being held and planned. In Beijing, some six thousand people crowded into the Workers' Gymnasium Thursday for a benefit concert by Hong Kong heartthrob Nicholas Tse. Also Thursday, top Finnish rockers shared the stage in Helsinki, collecting money for the Red Cross, and Norwegian stars held a free show in Stavanger, recording a benefit single.
One of the first big benefits in the U.S. - headlined by Willie Nelson - is set for Sunday in Austin, Texas.