In 1986, the original "Legend of Zelda" arrived on the Nintendo Entertainment System and, subsequently, spawned a decades-long blockbuster franchise.

The original game's open-world environment was massive at the time, and half of that world was hidden from players — it's known as the "minus world."

One intrepid YouTube creator managed to access to the game's minus world earlier this year. What he found is fascinating and bizarre.

The original "Legend of Zelda" for the Nintendo Entertainment System is a massive, open-world game — and it could've been even bigger.

That's because the game's voluminous open world was actually cut in half before the game's release; the lower half is known as the game's "minus world," where elements of the game could be tested by its developers at Nintendo.

Here's a look at what that means in practice:

The top half is the game's playable map. The bottom half is the "minus world." Nintendo/YouTube

The concept of an unplayable section of a game has been around for decades.

The original "Super Mario Bros." is known to have a glitch enabling players to access hundreds of hidden levels — many of which are full of bizarre, often broken elements — and it's far from the only one. Even modern games often contain elements that are hidden from players. Entire levels, enemies, bosses, and sections of story are relegated to these hidden places.

In the case of the original "Legend of Zelda," a full half of the game's open-world environment was employed as a minus world.

One of the strange-looking stages in the minus world of "The Legend of Zelda." Nintendo/YouTube

Through some code manipulation across several hours, one intrepid YouTube creator managed to break through the game's barriers and access the massive section of the game.

What he found, unsurprisingly, is mostly a mess.

That's because the minus world was never intended for players — it was an area where code could be tested before being implemented into the playable game. As such, enemies glitch into existence, text is often garbled, and some of the areas look like replicas of areas you may have seen in the game (albeit with weird aberrations). You probably don't want to play this stuff, as interesting as it looks.

That said, it's a fascinating look into a gaming classic during its creation — check out the full video right here: