It's no secret that the Avengers Tower of the MCU is a pretty cool building. While it was originally Stark Tower in The Avengers, Tony would transform and remodel the building to become the team's base of operations by Avengers: Age of Ultron. However, while Avengers Tower was quite the impressive structure in the MCU, it's nothing compared to the Avengers Tower in the Marvel Comics Universe, thanks to one incredible upgrade: vibranium.
Avengers Tower was first created in 2005's New Avengers from writer Brian Michael Bendis with art by David Finch. This new team of Avengers was created by Captain America and Iron Man as a new fresh start for the team, as the Avengers had been disassembled after the events of House of M and Wanda Maximoff's reality-bending psychotic break, which resulted in a handful of the Avengers' deaths. Rather than returning to Avengers Mansion in that story, the Avengers found a new space to hang their masks and capes. Realizing that he had an office building that no one was using due to its close proximity to the Fantastic Four's Baxter Building and fears of a resulting alien attack, Tony Stark was able to remodel the building as their new base of operations, giving it all the bells and whistles with one epic feature in particular to ward off said alien incursions.
The Avengers Tower in the comics was remodeled by Tony Stark using none other than vibranium-enforced concrete for both its interior and exterior walls. Vibranium, of course, is the very same metal that Captain America's shield is made of, as well as Black Panther's suit, and is Wakanda's most valuable resource due to its near indestructibility and versatile nature. As a result, Avengers Tower is extremely durable, resistant to attacks of any kind, making it the perfect place for the Avengers to regroup and rest (especially when there's usually a big "A" on the side of the building).
The Tower also features its own Quinjets, supposedly unbreakable windows (though Spider-Man did throw Wolverine out of one), and has plenty of space and amenities for permanent residency if individual members so choose. What fans might not know is that the Avengers only operate out of the top three floors, while the rest of the building is home to Stark's other philanthropic interests such as a children's hospital named for his mother and a clinic to help those with substance abuse, among other Stark subsidiaries.
While he thought of almost everything for Avengers Tower, Tony definitely didn't plan on his building being constructed around the Sentry's Watchtower. The Superman-level hero had been erased from the minds of Earth's populace at the time, meaning that while Tony's designs did take the existing structure into account, he wasn't conscious of that fact until the Sentry returned, transforming Avengers Tower from a high-tech skyscraper into something even grander. Thanks to Tony Stark, Avengers Tower would become a constant headquarters for Earth's Mightiest Heroes, and the impressive (and no doubt costly) addition of vibranium helped ensure that it would long be a fixture of Marvel Comics' New York skyline.