The Asian tsunami that crashed into coastal communities around the Indian Ocean on Dec. 26, 2004, is this century’s deadliest natural disaster so far.

The brunt of the tsunami was felt in the Indonesian province of Aceh, where 170,000 people perished. Sri Lanka, India and Thailand were devastated, too. More than a thousand miles apart, across the Indian Ocean, hundreds of coastal communities were united in their grief, and in facing years of rebuilding and regrouping.

Tearful mourners prayed Thursday as ceremonies began across Asia to remember the 220,000 people who died two decades ago when a tsunami hit coastlines around the Indian Ocean, in one