Fifteen years ago this week, Peter Jackson’s The Fellowship of the Ring premiered in theaters. The film opened to fanfare as the first installment of a long-awaited live-action adaptation of Lord of the Rings, J.R.R. Tolkien’s epic fantasy series. But in the years since, it’s clear that it was more than that. Lord of the Rings wasn’t just a movie adaptation of a beloved series. It would set a template that Hollywood has followed for years since — not just for epic fantasy, but the entire medium of film.

Since its release, there hasn’t been a production quite like The Lord of the Rings: an intense project that both adhered closely to the source material, but which also became an anchoring event in cinemas. Indeed, in the face of massive cinematic universe projects such as the Marvel, Harry Potter, or Star Wars films, a trilogy seems almost quaint.

Like the novels, The Lord of the Rings was essentially a single film split into smaller installments. Originally intended as a sequel to Tolkien’s debut The Hobbit, the novels are a story that grew in the telling, turning from a light-hearted fantasy adventure to a massive tome that would provide inspiration for almost every fantasy novel that followed it. The series had been adapted in the past with a series of animated films starting in 1977, but it wasn’t until the late-1990s that there was serious interest in doing a live-action version.

Jackson had initially planned for the adaptation to run for two films, with studios pushing for it to be condensed down to one. When the project landed with New Line Cinemas, studio head Bob Shaye somewhat famously asked, “Why would I want to do two films? There are three books. Why not do three films?” The expansion to become a trilogy would allow Jackson to adapt each novel, and to adapt more of Tolkien’s original material. Production for the film started in October 1999, with Peter Jackson helming an ambitious project: all three films of the series would be shot at the same time in New Zealand over a 438-day shoot, with additional reshoots.

The trilogy was an incredible success at the box office, and with audiences and critics. The films eventually earned a collective 17 Academy Awards, with the Return of the King picking up an Oscar for Best Picture and Best Director. The film’s success was also critical in kicking off the geek film renaissance that began during the early 2000s, which helped pave the way for a number of other adaptations of well-known fantasy novels, such as 2005’s The Chronicles of Narnia and 2007’s The Golden Compass. The trilogy’s success also demonstrated that fantasy was no longer for a niche audience, unleashing the floodgates for films such as Stardust, Snow White and the Huntsman, Clash of the Titans, and television shows such as HBO’s Game of Thrones, MTV’s The Shannara Chronicles, and Legend of the Seeker.

Even the manner of their production was imitated by high-profile blockbusters such as The Matrix Reloaded / The Matrix Revolutions and Pirates of the Caribbean: Dead Man’s Chest / At World’s End, installments which were filmed simultaneously. While this wasn’t new to the film industry, the risk that New Line Cinemas took on developing an entire untested concept is staggering.

Those nerdy books you read when you were a teenager became the hottest parts of popular culture. Fantasy tomes and ongoing series such as Terry Brooks’ Shannara Chronicles, George R.R. Martin’s Song of Ice and Fire series, and Robert Jordan’s Wheel of Time series gained new readers, while new fantasy epics such as Brian Staveley’s Chronicles of the Unhewn Throne and Brandon Sanderson’s The Stormlight Archive have begun to fill the void with new epics to explore. It suddenly became cool to be obsessed with a decades-old fantasy novel, to play Dungeons & Dragons, or dress up at conventions.

Lord of the Rings feels like it was this enormous cultural touchstone that made one’s geeky hobbies socially acceptable; even desired. I remember people being taken aback at the three to three-and-a-half hour runtimes for each film; now, binge watching a ten-hour television show feels commonplace. The trilogy endures, even a decade and a half after it first entered theaters, through marathon viewings and an endless supply of ‘One does not simply ...’ memes.

To date, there’s no project that feels quite like it has the same cultural footprint as those first Lord of the Rings films. They happened at the right moment, providing this massive cultural experience that only properties such as Star Wars or Star Trek had to that point provided. You can’t force a cultural phenomenon: everything just has to click into the right place. An excellent example of where this doesn’t work is Jackson’s own Hobbit series. While the series performed well at the box office, it never had the same impact on the world as the films that would precede it. Part of this was source material: Lord of the Rings had more than enough material to work with, while the Hobbit (to put it into Bilbo’s own words) felt “thin, sort of stretched, like butter scraped over too much bread.”

Moreover, these were films that never should have worked: they were massive in scale, were based on novels that were half a century old, and above all, were great films. A decade and a half later, and the film industry has taken to heart some lessons from their success: audiences are well versed in the language of science fiction and fantasy films, and it’s rare to see a film announced without it being couched as being part of some sort of larger property or franchise. In a time when we’re obsessed with super-connected cinematic universes, Jackson’s Lord of the Rings are the perfect reminder that however hard we try, these stories can’t be engineered, and that sometimes, the experience is just magical.