MIYAKO, Japan, 8 April (AP) — Modern sea walls failed to protect coastal towns from Japan's destructive tsunami last month. But in the hamlet of Aneyoshi, a single centuries-old tablet saved the day.

"High dwellings are the peace and harmony of our descendants," the stone slab reads. "Remember the calamity of the great tsunamis. Do not build any homes below this point."

It was advice the dozen or so households of Aneyoshi heeded, and their homes emerged unscathed from a disaster that flattened low-lying communities elsewhere and killed thousands along Japan's northeastern shore.

Hundreds of such markers dot the coastline, some more than 600 years old. Collectively they form a crude warning system for Japan, whose long coasts along major fault lines have made it a repeated target of earthquakes and tsunamis over the centuries. …

"People had this crucial knowledge, but they were busy with their lives and jobs, and many forgot," said Yotaru Hatamura, a scholar who has studied the tablets.

One stone marker warned of the danger in the coastal city of Kesennuma: "Always be prepared for unexpected tsunamis. Choose life over your possessions and valuables."

Tetsuko Takahashi, 70, safe in her hillside house, watched from her front window as others ignored that advice. She saw a ship swept a half-mile (nearly a kilometer) inland, crushing buildings in its path.

"After the earthquake, people went back to their homes to get their valuables and stow their 'tatami' floor mats. They all got caught," she said. …