When a massive tsunami engulfed the north-eastern coastline of Japan a decade ago, it wiped out everything in its path, flattening villages, killing nearly 20,000 people and triggering a nuclear meltdown.
The old seawalls which had been built along the coastline to protect villages and infrastructure offered little protection.
Presented by former Japan correspondent Mark Willacy, The Great Wall of Japan ravels along the north-eastern coast of Japan's main island to meet the fishermen and communities affected by one of the country's biggest ever construction projects. More details
Today, the government's solution to the next tsunami is to build an even bigger and longer seawall to protect Japan's coastal communities.
Up to 14 metres high and 400 kilometres long, the new seawall is dividing communities, and some fear, placing them in greater danger.