• The Empire State Building is known for its panoramic views of New York City, but visitors don't always have the right vantage point to appreciate the architecture.
• A new observatory on the building's second floor celebrates the construction of the skyscraper, which was completed in 1931. 
• At the observatory's entrance, a 20-feet model helps visitors see the handiwork that has kept the building sturdy for decades.
• To move the model into the building, engineers had to carve a hole in the second level.
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On a cloudless day, visitors at the Empire State Building can see up to 80 miles of skyline from their vantage point in Midtown Manhattan. It's one of the biggest draws of the iconic skyscraper.

Now a team of designers, developers, engineers, and architects are encouraging visitors to look inward with a new observatory that opened on July 29. 

Read more: 14 weird facts that you probably didn't know about the Empire State Building

At the observatory's entrance stands a 20-foot model of the building that straddles two floors. To get the model to fit inside, engineers had to carve a hole in the second level.

While peeling back the layers of the structure, they unearthed some treasures from its past.

The Empire State Building was erected in 1931 in the middle of the Great Depression. Engineers say it's an impeccably constructed skyscraper.

The site was once home to a Waldorf-Astoria Hotel, which was torn down to make way for the $40 million icon. To build the 102-story skyscraper, contractors sourced materials from all over the world, including steel from Pittsburgh, wood from the Pacific Coast, and marble from Italy, France, and England. 

Thousands of workers toiled daily to bring the building to life, with some of them facing safety risks.

If just one worker didn't show up to the construction site, it could derail an entire day's production. At least five people died on the job. 

Almost 90 years later, a model at the observatory's entrance reveals the intricacy of the building, which has more than 6,500 windows.

The 20-foot replica of the Empire State Building was built by master model maker Richard Tenguerian.

Tenguerian said he was used to designing models from scratch, so recreating an iconic building required extra precision. Together with his team, he hand-measured the Empire State Building, then used 3D printing to create his replica.

Both the skyscraper and the replica use the same lighting technology, so when the Empire State Building lights up red, white, and blue, the model does, too. 

At 20 feet high, the model was taller than the first floor of the building, so engineers had to carve a hole in the floor above.

Engineers also had to check that the ground floor was sturdy enough to hold the replica, which weighs 1,274 pounds.

Read more: How a 2.5-story model of the Empire State Building is made

They also chipped away at concrete columns to reveal the original steel beams.

The observatory's lead engineer, Sergio Londono, said the building is sturdier than others constructed during the same era. 

The observatory features an old elevator system that used to control the speed of an elevator car. Original visitors paid $1 to ride the elevators to the observation decks.

The skyscraper's elevators are designed to whiz up and down at 1,200 feet per minute. The original versions used a mechanical system to control the speed of elevators, direct them to specific floors, and determine when doors opened and closed.

In 2011, the same company that built the original elevators, Otis Elevator Co., helped install new computer-controlled versions.

In 1945, a military plane accidentally crashed into the north side of the building, causing an elevator cable to snap and a woman to fall 75 stories in her elevator car. She later earned the Guinness World Record for the longest fall survived in an elevator. 

As an older skyscraper, the Empire State Building is undergoing constant renovation, but it was also built to last.

Londono said the building will remain in good shape for at least another 100 years. 

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