If you’re getting anxious waiting for the final season of Game of Thrones and need a dose of dark high-quality drama to fill in the time, you may be interested in HBO’s frequently overlooked production, Oz.

Oz was the first major TV drama made by the HBO network, spanning six seasons from 1997 to 2003. It is set in the fictional prison of Oswald State Penitentiary, leading to the nickname ‘Oz’. The show mainly focuses on an experimental wing of the prison dubbed ‘Emerald City’, another ironic reference to the famous film ‘The Wizard of Oz’. Rehabilitation and education are emphasised in this block, but with added rules and conditions. Emerald City is overseen by unit manager Tim McManus (Terry Kinney), an idealist who wants to make Emerald City a model for the wider prison system. And as you may expect, it doesn’t go quite to plan.

Each episode has a distinct theme, which is articulated by narrator and wheel-chair bound inmate, Augustus Hill (Harold Perrineau). These themes range from love, revenge, prison life and the human mind. Hill’s narration scenes break the fourth wall and often have a dream-like tone, further distancing Oz from the regular world- and subsequently giving it a fitting nightmarish vibe.

Oz is a brutal, unflinching depiction of life in a maximum-security prison. It does not shy away from disturbing content such as violence, racism and drug abuse. While the violence is occasionally exaggerated for dramatic purposes, the show skilfully portrays a suffocating climate of 24/7 paranoid vigilance and fear. Moreover, this is a long way from the Shawshank Redemption.

None of the prisoners featured are innocent men who were wrongly convicted and ultimately are vindicated – all the inmate characters deserve to be there. Having said that, some are certainly easier to sympathise with than others. A handful express sincere remorse, but most are simply concerned with staying alive or undermining their rivals. The prison staff vary in their decency as well. Some are genuinely trying to make the world a better place, some are just trying to survive, and others only differ from the inmates by the fact they can leave at the end of the day.

One of the show’s best strengths is the complexity of the featured characters and story arcs. Like other HBO dramas, you are often left with conflicting feelings on many individuals. The quality of the writing and acting abilities of the cast humanises even the most loathsome characters. And vice versa, many of the more relatable characters have very clear flaws.

Many of their actions are difficult to judge given the unforgiving world they find themselves in and there’s rarely straightforward dilemmas with easy resolutions. Well-meaning characters can be frustratingly short-sighted, bad characters are at times legitimate victims of injustice.The creator of the show, Tom Fontana, summed up in an interview how the characters were written: “What HBO said to me was ‘We don’t care if they’re likeable, as long as they’re compelling’.”

Again, the quality of the acting is outstanding. Many of the featured cast were either established theatre actors or went on to play major roles in other long-running TV series, including HBO productions such as Band of Brothers, The Sopranos and The Wire. Several went on to have leading roles in highly acclaimed films. The focus and commitment behind the performances in Oz is some of the most intense you’ll see in TV drama. This intensity even led to real-world consequences-J.K. Simmons (who won an Oscar for his work in Whiplash) revealed that he was briefly depressed as a result of playing the hate filled Neo-Nazi leader, Vern Schillinger. Additionally, some of the cast were actual ex-convicts as Fontona wanted the show to have authenticity. Fontona was so dedicated to creating a realistic atmosphere on set that he even volunteered to get a tattoo of the show’s name on his arm, which was filmed and used as part of the opening credits.

Though arguably the main selling point of Oz is that it set the standard for the network TV serial drama. Many of the elements that make up contemporary shows were at least partially influenced by Oz. Moreover, it paved the way for other shows in depicting controversial content. Without Oz, many other great shows may never have gotten off the ground.

So, if you’re already a fan of HBO and you want gritty realism and gut-wrenching drama in the harsh setting of a prison, look no further than Oz.

It may not have dragons, but it has plenty of monsters.