Huge reflecting pools, waterfalls, skyscrapers and a cavernous underground museum under construction help make the National Sept. 11 Memorial and Museum at the World Trade Center an awesome spectacle.

But all that eye-welling magnificence comes with a jaw-dropping price tag. The foundation that runs the memorial estimates that once the roughly $700 million project is complete, it will cost $60 million a year to operate.

The anticipated cost bothers some critics and raises concerns even among the memorial's allies that the budget may be unsustainable without a hefty government subsidy.

FULL COVERAGE: 9/11/01:  Eleven Years Later

Officials at the memorial say they face unique challenges that make comparisons to other national memorials difficult. The foundation plans to spend at least a fifth of its annual operating budget, or around $12 million, on security because of terrorism fears.

(Copyright 2012 by The Associated Press. All Rights Reserved.)