When the Woolworth Building was constructed in 1910, owner Frank Woolworth and architect Cass Gilbert wanted to make the structure fireproof. With the recent tragedy of Triangle Shirtwaist Fire and the memory of the Great Fire of New York City in 1835 in mind, every precaution was taken to ensure that the “Cathedral of Commerce” would not succumb to a similar fate.

Fires are always destructive, and in cities where buildings are close together and fire can spread quickly, they can be devastating.  From carefully chosen construction materials to innovative new technologies, here are five places you can spot the fireproofing methods used in the Woolworth Building.

5. Terra Cotta in the Walls of the Woolworth Building

Image via Wikimedia CommonsLibrary of Congress

The Woolworth Building is one of the first skyscrapers to be constructed with steel. For further fire protection, the steel beams that make up the building’s skeleton are wrapped in terra cotta, a clay that does not burn. Terra cotta was also used by Gilbert in his design of the nearby building at 90 West Street. 90 West was severely damaged and caught fire in the terrorist attacks of 9/11, but due to the terra cotta, the spread of the fires was contained and though chunks were missing and the inside had to be gutted, the building was structurally sound.

Exposed terra cotta in the basement of the Woolworth Building

The lower levels of the Woolworth Building’s exterior also contain limestone, which is another type of stone that does not burn. No flammable materials were used in the construction, which helped give the Woolworth a sort of automatic fireproofing. On a tour of the Woolworth Building, you can see an exposed portion of the wall where the terra cotta is visible.