They came to Lower Manhattan from around the world to visit the 9/11 Memorial on an unseasonably warm winter day. They came to see where it had happened — where terrorists had crashed two jetliners into the World Trade Center towers, destroying them in horrific plumes of ash, flames and pulverized concrete.

But many did not realize they were also visiting the site of an earlier attack that, while less deadly, presaged an era of terrorism fears in New York City that many believe culminated in September 2001.

It has been almost 24 years since the Feb. 26, 1993, World Trade Center bombing that killed six people and injured around 1,000, and many who gathered outside the 9/11 Memorial on Sunday had no knowledge of the attack or the fiery speech of the man — Omar Abdel Rahman — who the authorities believe inspired it.

Mr. Abdel Rahman died on Saturday in a federal prison in North Carolina where he was serving a life sentence for his role in plotting a broad terror campaign in New York that was never carried out.