Beginning today, visitors can place free online reservations to tour the 9/11 Memorial site which will open to the public on September 12, 2011.

The free timed entry passes will be required for visitors to gain security clearance into the Lower Manhattan memorial.

The free online passes can be secured up to six months in advance of a visit. A limited number of reservations will also be made available at the Preview Site on nearby Vesey Street.

Officials say the memorial can handle about 1,500 visitors at one time with an estimated 4 million people expected to visit during its first year of operation.

Source: USA Today