by KYW's Karin Phillips

A celebration was held Monday morning in Philadelphia, as its City Hall was recognized for being one of the most unique buildings in the United States.

City Hall, which was opened in 1901 after 30 years of construction, has been named a National Historic Civil Engineering Landmark by the American Society of Civil Engineers. 

Jonathan Farnham is acting city historic preservation director:

"We all know that this is a great building from an architectural and artistic perspectives, but you can't really see the engineering that went into the building."

Dennis Martenson is national president of the ASCE:

"It is with great pleasure that I am able to recognize a project that presents the wisdom of civil engineers and embodies meticulous principles of structural engineering."

A plaque acknowledging the historic award is now installed in City Hall's east portal.