The National September 11 Memorial & Museum in New York City stands as a place of remembrance and a somber tribute to those killed in the 9/11 terrorist attacks. Reopened 10 years after the 2001 attacks, the eight-acre (3.2-hectare) plaza—built on the World Trade Center site—features two massive square reflecting pools whose waterfalls cascade down into the footprints of the former Twin Towers. The surrounding plaza is a peaceful and moving green space, while the museum, located beneath the plaza, lends a deeper understanding to the impact of that day. You’ll undoubtedly leave with a heavy heart.