As the country marks the 15th anniversary of the Sept. 11, 2001 terrorist attacks , a multisite photography exhibition looks at how the World Trade Center and its absence has defined New Yorks skyline over the decades.

Camilo Jos Vergara moved to New York City in 1970. He grew up in Rengo, Chile a town where the tallest building was a three-story post office, he said. Vergaras arrival coincided with the construction of the Twin Towers, and he has routinely photographed the site for the last 46 years.

I saw the soaring towers as a symbol of a new world emerging, Vergara wrote in a recent essay . From up close, they simultaneously attracted and repelled me: I saw them as a place of exclusion, where the contradictions of wealth and poverty were extreme. But from afar the buildings were transformed. They became a place where ordinary people could dream that the skyline was theirs.