The Pentagon Memorial
It's a permanent outdoor memorial to those who died as victims in the building of the 9/11 attack. The memorial opened seven years after the attack. The memorial is open seven days a week all year, and is also the only place on the pentagon's grounds that photography is allowed. To honor the anniversary each year, and american flag is hung on the section of the pentagon that was hit by flight 77, at night this section of the building is lit up in blue. On the fifth anniversary, there was a light show of 184 lights from the center of the courtyard.