On December 26, 2004 a 9.3-magnitude earthquake off Indonesia's western tip generated a series of massive waves that pummelled the coastline of 14 countries as far apart as Indonesia, Thailand, Sri Lanka and Somalia.
Among the victims were thousands of foreign tourists enjoying Christmas in the region, carrying the tragedy of an unprecedented natural disaster into homes around the world.
A chorus of voices singing the Indonesian national anthem opened the official memorial at a 20-acre park in Indonesia's Banda Aceh - the main city of the province closest to the epicentre of the massive quake and which bore the brunt of waves towering up to 115 feet high.
"Thousands of corpses were sprawled in this field," Indonesian Vice President Jusuf Kalla told the crowd of several thousand - many among them weeping.
"Tears that fell at that time... there were feelings of confusion, shock, sorrow, fear and suffering. We prayed.
"And then we rose and received help in an extraordinary way. Help came from Indonesia and everyone else, our spirits were revived," he said, hailing the outpouring of aid from local and foreign donors.
Mosques also held prayers across the province early today while people visited mass graves - the resting place of many of Indonesia's 170,000 tsunami dead.
But a Red Cross display of hundreds of salvaged ID documents and bank cards, also served as grim reminder that many victims simply vanished.
In southern Thailand, where half of the 5,300 dead were foreign tourists, a smattering of holidaymakers gathered at a memorial park in the small fishing village of Ban Nam Khem, which was obliterated by the waves.
As the ceremony began, survivors recounted stories of horror and miraculous survival as the churning waters, laden with the debris of eviscerated bungalows, cars and boats, swept in without warning, killing half of the village's inhabitants.
Swiss national Raymond Moor said he noticed something was amiss when he saw a white line on the horizon rushing towards the beach where he and his wife were having breakfast.
"I told my wife to run for her life... it wasn't a wave but a black wall," he said, describing being caught up in the water moments later like "being in a washing machine".
"A Thai woman from the hotel saved my life by pulling me up to a balcony. She died later," he said, breaking into tears. Moor's wife survived.