Washington Monument : Though admission into the monument is free, tickets are required and long lines form to get inside every day. A better bet: enjoy the exterior of the monument from the steps of the Lincoln Monument, or from the tidal basin during the National Cherry Blossom Festival in April.
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U.S. Marine Corps War Memorial (Iwo Jima Statue) Washington, DC. I've been here such a cool memorial.
Monument Valley, Utah and Arizona - Straddling the Utah and Arizona border on a Navajo Tribal Park, this vast desert valley is punctuated by red siltstone buttes sculpted by the wind into hand-like shapes known as “mittens.”