Twenty years ago today, Heat—an almost three-hour-long epic heist film starring Robert De Niro and Al Pacino—was released into theaters. Written and directed by Michael Mann, it featured no special effects, was filmed in 65 real locations around L.A. (no soundstages), and approached its material with a kind of realism rarely seen in films before or since, which is one reason why many critics and fans consider it to be one of the greatest crime dramas of all time. Here are 15 burning facts about this seminal movie.

1. IT’S BASED ON A MEETING BETWEEN A REAL-LIFE DETECTIVE AND A BANK ROBBER.

In 1963 a Chicago detective named Chuck Adamson dined in a Chicago coffee shop with convicted bank robber Neil McCauley—the same name as De Niro’s character. As Den of Geek tells it, a year after the fated meeting, Adamson tracked McCauley and his crew to an in-progress supermarket heist. A chase ensued and McCauley was shot on a front lawn. Adamson befriended Michael Mann when they worked together on Thief and Crime Story, but the genesis for Heat came from the idea of two men who are on opposing sides of the law coming together and understanding each other.

2. AMY BRENNEMAN WAS AGAINST TAKING A ROLE IN HEAT—BECAUSE OF THE GUNS.

The actress, who played De Niro’s love interest Eady in the film, almost wasn’t in it. Mann had seen her on NYPD Blue and gave her the script, “which was a lot of boys and guns.” Coming from a liberal background, Brenneman didn’t think the role was right for her. “I said, ‘I don’t want to do men and guns,’” she recalled to the Huffington Post—but Mann still wanted to meet with her. “I said okay, I don’t think of myself doing this movie. At that point I was reading for Ashley Judd’s part. So I came in and Michael Mann said, ‘I hear you don’t like my script.’ He said, ‘Why?,’ and I said, ‘I’m sick of men and guns. I don’t understand why they don’t sit down and talk.’ And Michael said later I’m the one person in that movie, going like, ‘Who are you people?’ He realized at that point I had to play the part."

3. ONCE MANN FIGURED OUT THE ENDING, THE STORY FELL INTO PLACE.

Though he’d written the script for Heat more than a decade before it reached the screen, the original ending troubled Mann. In particular, he couldn’t figure out the best way to resolve the relationship between Hanna and McCauley. “What I came to later was to the perfect equivalence of the connection,” Mann told an audience during a 20th anniversary screening at this year’s Toronto International Film Festival. “It occurred to me that Neil was fortunate enough to die in contact with the only other guy on the planet who was really similar, almost like him, and understood him totally. That became the end of a dialectic, which I then reverse-engineered into a lot of previous scenes which preceded it. I could build off that final moment.”

4. THE IDEA TO PAIR DE NIRO AND PACINO CAME DURING A BREAKFAST MEETING.

Producer Art Linson and Mann had breakfast at the now-closed Broadway Deli in Santa Monica, where McCauley and Eady meet in the film. Mann asked Linson if he wanted to co-produce the film with him. “And he said, ‘You’re out of your mind. You’ve got to direct it.’ Then we came up with the idea of Bob and Al. Who were the best people we could imagine for these parts? It was Bob and Al.”

5. THE RESTAURANT WHERE DE NIRO AND PACINO FINALLY MEET CLOSED LAST YEAR.

For nearly 30 years, Kate Mantilini in Beverly Hills was a well-known gathering place for Oscar voters and star-studded movie premiere after-parties. But because of rising rents, the owners decided to close the restaurant last year. The now-iconic scene between McCauley and Hanna was filmed there, and was commemorated when the restaurant hung a blown-up still from the scene on the wall.

6. MANN DOESN’T CONSIDER HEAT TO BE A GENRE FILM.    

Sure, it’s about bank robbers and has two protagonists in opposition to one another and some chase scenes, but as Mann told Deadline, “The most important parts to me were these choruses where you take everybody home.” Mann talks about how the viewer sees Neil McCauley’s home life, and both Hanna’s and Val Kilmer’s conflicted marriages at their respective homes. “Then you go back to the plot drive of the crime story, the police story. And then you’re back again. So the real engine is the people, the characters. It’s not really a genre film.” 

7. XANDER BERKELEY IS THE ONLY ACTOR FROM HEAT WHO ALSO STARRED IN L.A. TAKEDOWN.

Before there was Heat there was L.A. Takedown, a television movie (originally intended as a two-hour series pilot) from which Heat evolved. Xander Berkeley is the only actor to appear in both projects: in L.A. Takedown he played Waingro, and he took the role seriously. In fact, he got so into the psychotic character that he got hives and had to go to the ER. “I just thought, ‘Wow, that’s dark stuff. I think I’ll steer completely clear of that in the future,’” Berkeley told The A.V. Club.

Berkeley knew he’d have to play a similar role when the opportunity to appear in Heat came around, but he’d been offered a part in the Pamela Anderson film Barb Wire and wasn’t available. Kevin Gage played Waingro in Heat, but Mann was able to convince Berkeley to play the smaller role of Ralph, against Pacino. “I felt greatly honored to have been the only one to be a part of both projects,” Berkeley said. 

8. THE HOME WHERE DANNY TREJO DIES IN THE MOVIE HAS A LARGE BLOOD STAIN UNDER THE FLOORBOARDS.

The East L.A. house on stilts where McCauley kills Trejo (Danny Trejo) was featured in Heat: Return to the Scene of the Crime, a DVD featurette. A camera crew visited the family that lives there now, who said they knew it was “The Heat House” when they bought it. In the movie, McCauley shoots Trejo and a pool of blood forms around his dead body. Sure enough, the owners pulled up the carpet and were surprised to find the fake blood stain, which is a rather bright red, not brown like real blood. “A little piece of [the] history of Heat right there under the floorboards,” homeowner Jayme Mazzochi proudly stated.

9. MANN PICKED THE AIRPORT FOR THE CLIMAX BECAUSE IT LOOKED "SURREAL."

The ending takes places in an abandoned field near an airport, outside of the city. “I wanted to find a landscape that was so transient that it started to achieve a surreal effect on you but still maintained the gritty reality of the movie,” Mann told Deadline. “For me, it’s always the couple hundred yards before the runway starts at airports. Most people don’t go there; it’s a place where transients populate. There are towers, those orange and white buildings. I’m just attracted to places like that. The edge of runways, with those blue lights in them for example, they’re quite beautiful at dusk or at night. They’re part of our urban landscape but they have an unusual quality.”

10. DESPITE BEING IN THE SAME FILM, PACINO AND JON VOIGHT HAVE NEVER WORKED TOGETHER.

The actors didn’t share any scenes together in Heat, and somehow throughout their veteran careers they haven’t gotten around to appearing on-screen together. When Maxim asked Voight which actor he most wanted to work with, living or dead, he said Pacino. “I really love Al’s work, and himself, and we’re friends … so that would be something that would be fun for me to do. I like the audacity of his work, and the greatness of his work. I’m very aware of it.”

11. DE NIRO HELPED TOM SIZEMORE GET SOBER.

Tom Sizemore’s personal struggles with drug abuse and domestic violence have been well documented. But after working together on Heat, Sizemore and De Niro became pals, and one night De Niro tried to intervene. De Niro told Sizemore he needed to stop using heroin, and drove him to his private plane in order to get him the help he needed. “It was magical,” Sizemore told The Independent. “I watched this guy in the dark when I was 14 and wondered who he was. And here he is. I’m in his car and he’s driving me to the airport, he’s telling me that the gig is up, he’s telling me I’m a wonderful actor, that he’s not gonna let me die. ‘I love you,’ he told me, 'like you’re my son.' I didn’t wanna go, but I couldn’t say no to him.”

12. VAL KILMER’S GUN-HANDLING SKILLS WERE IMPRESSIVE.

One of Heat’s most iconic moments is the climactic 10-minute shootout scene, which was filmed every Saturday and Sunday in downtown L.A. for six weeks. The actors trained with men from the British Special Air Service (SAS) and at the L.A. County Sheriff’s combat shooting ranges. “We did everything for real,” Mann told Deadline. “[The actors] got so good that the footage of Val Kilmer, firing in two directions and doing a reload without a cut, they used that at Fort Bragg for Special Forces training.”

13. AFTER HEAT CAME OUT, COPYCAT CRIMES OCCURRED ALL OVER THE WORLD.

It’s unclear whether criminals had seen the film and were trying to mimic it, but in Cali, Colombia in 2003, 18 masked robbers drove a bus into an armored van and stole $350,000 in cash, which mirrors a scene in Heat. In 1997, a 44-minute shootout occurred in North Hollywood in which the gunmen, Emil Matasareanu and Larry Eugene Phillips, Jr., robbed a Bank of America wearing heavy body armor and carrying assault rifles. The shootout ended with both gunmen dead— Matasareanu was shot 29 times and wasn’t given any medical attention. It was later revealed that the gunmen had cited Heat as an influence for the robbery.

14. VAL KILMER’S IDEA FOR HEAT 2 ENTAILS ROMANCING NATALIE PORTMAN.

During a 2013 appearance on Larry King’s Hulu show, Kilmer—who played Chris Shiherlis in Heatshared his idea for a potential Heat sequel. “You remember Natalie Portman in it? She’s Pacino’s adopted daughter, so she comes home and says, ‘Daddy, daddy, I want you to meet my fiancé.’ And it’s me. He’s retired and I come to Chicago where he’s retired back to and I’m going to torture him, and then I’m going to kill him.” It's worth noting that Portman was only 14 years old when Heat came out, and Kilmer was 35.

15. HEAT IS ONE OF BEN AFFLECK’S FAVORITE HEIST FILMS.

For The Town, the 2010 bank robbery heist movie that he co-wrote, directed, and starred in, Ben Affleck found inspiration in Heat. “A movie hasn’t been made since that has a deeper feel of authenticity,” Affleck told The Daily Beast of Heat. “It feels so real that bank robbers then copied Heat. And when I was interviewing people in prison they referenced Heat. And when I was interviewing the FBI, they referenced Heat. So, aside from feeling bummed out that I’d always be in the shadow of Heat, I can certainly tell you, for sure, with great authority, that Heat is the one movie that’s cited as the real thing by people who really do that stuff."