A man was rescued Thursday morning by firefighters after he tumbled into a 10-foot-deep hole that opened up in the sidewalk along Seattle's downtown waterfront, one of the city's most popular promenades and tourist attractions.

The 60-year-old man reported minor back pain and was taken to Harborview Medical Center to be examined, Fire Department spokeswoman Dana Vander Houwen said.

The sidewalk, atop the deteriorating sea wall that separates Alaskan Way from Elliott Bay, is at the southern end of a walkway strolled by thousands of people daily.

City officials have long urged that the sea wall be fixed, and a new wall is planned as part of a $4.2 billion project to replace the Alaskan Way viaduct with a tunnel by 2015.

The hole, about 2 to 4 feet wide and 7 feet long, opened up without warning about 8 a.m. at a small park at the foot of South Washington Street in the city's historic Pioneer Square neighborhood.

The park is just south of the Washington State Ferries terminal that links downtown Seattle with the west side of Puget Sound.

In the mid-19th century, the land beneath the sidewalk was mud flats and near a sawmill at the foot of Skid Road, the one-time path where logs were skidded downhill and that later became a generic term for down-and-out neighborhoods.

Vander Houwen said 26 firefighters worked to rescue the man, blocking heavily used Alaskan Way during the morning rush hour.

There was a hollow space beneath where the 4-inch-thick sidewalk gave way, she said. "He was trapped by some of his clothing and backpack."

The man cut off a sleeve that was snagged in the hole as firefighters drilled bolts into nearby concrete, fastened ropes to the bolts and lowered pieces of wood and inflatable air bags to stabilize the soil.

Ladders were extended across the opening, and the man was placed into a harness and pulled to the surface after about an hour, Vander Houwen said.

The walkway will remain closed to pedestrians until it can be further examined, she said.

In late 2005, Mayor Greg Nickels said small marine creatures were boring through the sea wall so rapidly that city divers had to increase the frequency of inspections of the wood and steel structure to twice a year.