The more you progress through Subnautica, the more you’ll learn about the game’s real story, what is going on with Planet 4546B, and what you’ll need to do to escape from it. The game will take you down a path where you’ll eventually come face to face with the gargantuan Sea Emperor Leviathan, a creature so big, old, and wise it even has telepathic abilities.

But before you can meet this leviathan and free it from the facility where the Precursor Race imprisoned it, you’ll have to find a way to enter the Primary Containment Facility, an Alien Base located in the Lava Lakes area. To enter the place, you’ll need a Subnautica Blue Tablet to gain access. Here’s where to find it.

Updated September 28, 2021, by Miguel Amaro: If you want to complete Subnautica’s storyline, you’ll have to find the Blue Tablet. Doing so is pretty straightforward, but getting lost in the dangerous Inactive Lava Zone is very easy. This guide has been updated with more info and pictures so you can safely traverse this cavernous biome​​​​​​.

The Blue Tablet

There’s only one Subnautica Blue Tablet location since there’s only one in the whole game. If you need more, you’ll have to craft them, but let’s not get ahead of ourselves. The original Blue Tablet will be available in the Alien Thermal Plant.

The facility where the Subnautica Blue Tablet is located is another one of the Alien Bases built by the Precursor Race a long time ago. Out of all the bases, The Alien Thermal Plant is the smallest one, and you’ll find it in the Inactive Lava Zone cavernous biome, more precisely in the Lava Castle.

  • Keep in mind that to get to this zone, you’ll need a vehicle that can dive to the bottom of the ocean, so before looking for Subnautica Blue Tablet, make sure you have a Cyclops and a Prawn Suit available.

How To Find The Purple Tablet

Before getting to the Blue Tablet you’ll have to unlock the doors along the way. To do this, you’ll need another one of Subnautica tablets, the Purple Tablet.

It’s very likely that you’ve already found a purple tablet and know how to craft it by that point in the game. There are seven purple ones in total, and you can find them in:

  • The Floating Island, at the Degasi Seabases Mountain Island Mountains Caves Quarantine Enforcement Platform

After scanning the broken Purple Tablet (which will be in front of the Quarantine Enforcement Platform’s land entrance) you’ll be able to craft it in the Fabricator using one Ion Cube and two Diamonds (a raw material you’ll find in shale outcrops or as free-floating diamonds).

Where To Find The Blue Tablet

To get to Subnautica Blue Tablet Location, find the Lava Castle and search for a cave entrance. Be careful though, as there’s a fire-spitting leviathan roaming the area.

After entering the cave, go through the tunnels till you reach the center of the area (you’ll know you’re there because there’s a huge Alien structure impossible to miss).

There’ll be aggressive creatures roaming the area, so try to avoid them.

From there, all you have to do is swim towards the top and to the side until you find an entrance. Then go inside.

Once you’re inside the Alien Thermal Plant, you’ll see there are two locked doors. Behind the first one is the object you’re looking for, the Subnautica Blue Tablet.

The other unlocks the path towards the facility’s main generator as well as three data terminals.

After scanning the Blue Tablet, you’ll be able to craft it in three seconds using the Fabricator and the following materials:

  • x1 Ion Cube: a piece of tech that the Precursor Race created. You’ll find these cubes in Alien Bases or Some Alien Caches. Also, there are Large Ion Cube Deposits in the Alien Thermal Plant and the Primary Containment Facility. x2 Kyanite: a raw material found in the Inactive Lava Zone, Lava Lakes, and Lava Castle biomes.

NEXT: Subnautica: Incredibly Useful Hidden Items and Where To Find Them