the base of the building, which illuminated only the first three floors. Top of the World An enclosed observation level on the 27th floor, called "Top of the World", provides a 360-degree panoramic view of the city. The Top of the World is handicap accessible, offers Baltimore history, rotating art exhibits, occasional special events, a gift shop featuring local art, and is home of the 9/11 Memorial of Maryland. The observation level is open to the public during daytime hours, and may be rented for special events by government organizations and corporations. Impact of September 11 attacks Two hours after the September 11, 2001 attack on the World Trade Center in New York City, Baltimore's World Trade Center was evacuated and closed. This was a response to a "credible" threat that the Baltimore building would also be attacked. A resident of southwest Baltimore was arrested that night and accused of giving the police a false warning. Unsubstantiated bomb threats received on September 12 and September 14 further contributed to security concerns at the building. A temporary barrier of concrete walls was erected around the brick plaza between the building and Pratt Street, closing the area to pedestrian and vehicle access. Four barges were moved to the building's harbor side to protect it from attack by boats. Due to the building's name and its prominent location on Baltimore's skyline, state officials presumed that a similar attack on other American cities would likely target the Baltimore World Trade Center. Their response was criticized, because "such drastic steps" were not taken at world trade center buildings in other cities. As security was relaxed later in the year, the concrete barriers and barges were removed. The exterior lighting system was turned off and remained dark until the end of 2007. The waterfront walkway beneath the building, an extension of the Harborplace promenade, is now only open to the public during daylight hours. 9/11 Memorial of Maryland at Baltimore's World Trade Center A memorial to the victims of the September 11, 2001 attacks, built on the pedestrian promenade of the Baltimore World Trade Center between the building and Pratt Street, was dedicated on September 11, 2011, the tenth anniversary of the attacks. The memorial structure includes three 22-foot long steel beams from the New York World Trade Center, which were part of the 94th to 96th floors of the north tower. Twisted and fused together,