How To Reach The Underground In Blue Prince

Do you want to reach the Underground in Blue Prince? There's a massive area far below the mansion, and there are multiple ways to get there. Our guide discusses all these methods, as well as what you can expect once you've made it to the new location. Of course, this article does contain spoilers, too.

How to reach the Underground in Blue Prince

The Underground has various entrances, and you're likely to use all of them at least once in your playthrough. The most common paths, however, are via the Foundation or the Fountain/Blue Flame.

Note 1: The main sections are locked behind doors that can only be opened using the Basement Key. You have to reach the Antechamber to get it, and then bring it all the way to the Underground.

Note 2: Each day/run, the Basement Key will return to the Antechamber. However, any door you've opened using it will remain permanently unlocked even if it's no longer in your inventory.

Underground map

The map above shows the Blue Flame Underground zone. As you can see, there are five entranceways: Foundation, Fountain, Cliffside, Tomb, and Blue Flame.

Your main objective here is to reach the section with the Rotating Gear and the North Lever, as that path allows you to gain access to Room 46.

Foundation entrance

The Foundation became our primary way of reaching the Underground in Blue Prince. We do have a separate guide detailing the Foundation's placement and elevator activation, but here's the gist:

• The Foundation is unique in that you only need to place it once in the manor and its position will never reset with each run.
• Placement is important, since it determines if it's easily accessible or if you still need to draft a path to it.
• We placed our Foundation just past the Entrance Hall, so we only had to step once into it to go down the elevator to the Underground.
• Don't forget the Basement Key since you need it to open the door to the larger chamber beyond.

Fountain entrance

You can also access the Underground if you manage to drain the Fountain. Past the door opened by the Basement Key, you should see a mine cart blocking a narrow tunnel that leads to the Rotating Gear area and the Foundation (i.e. eastern) side.

• If you push the mine cart to the far end, it'll be tougher to reach the Rotating Gear/North Lever section via the Foundation entrance.
• If you pull the mine cart back all the way back, it'll be harder to reach the Rotating Gear/North Lever section via the Fountain entrance.
• Either way, push/pull the mine cart depending on which path is easier to access in your playthrough.

Cliffside entrance

Another method to reach the Underground in Blue Prince involves the Cliffside entrance. You should see a collapsed tunnel if you go down the steps from the manor yard/grounds. You need a Power Hammer to destroy the obstacles and weakened walls. This should lead you to the Basement, which also connects to the nook below the Foundation elevator.

Tomb entrance

One more option for the Underground exists, and but it's heavily based on RNG. Basically, you need to draft the Tomb in the outer room. Here's a quick summary:

• You must open the Garage Door to permanently gain access to the West Gate Path.
• Interact with the shed to see the drafting options. The Tomb may randomly appear as one of the choices.
• Solve the Tomb Puzzle based on the clues found in the Chapel.
• When you leave the Tomb, you'll find yourself near the aforementioned mine cart.

Blue Flame entrance

Finally, you can gain another entryway once you've activated all four Blue Flames in the grounds. Doing so causes an elevator to appear.

• The elevator takes you to a narrow tunnel, which is near the Chess Puzzle.
• There are spiral steps leading to an upper section. However, you might need to use the Burning Glass or Self-Igniting Torch while in the Fountain section just to make your way through.

The Reservoir: Traveling between the eastern and western banks

The mine cart blocks the tunnel that connects the eastern and western halves of the Underground, which is really annoying. However, you can travel between these areas (without using the other entrances) via the Reservoir:

• The Reservoir needs to be at certain water levels if you want to sail the boat to other locations.
• You may also fully drain the Reservoir to find goodies.

The Rotating Gear Puzzle and the Red Door

The task to complete the Rotating Gear Puzzle in Blue Prince is fairly straightforward. You just need to interact with the control mechanisms so you can cross the gap. The first mechanism is closer to the Foundation side, and you'll just make your way around the area as you go along.

• The most notable loot here is the Mechanarium blueprint, which lets you draft this special room. And, yes, there's also a Mechanarium Puzzle in that chamber.
• There's a full map of the Underground--i.e. the same one that we included earlier in this guide.
• Once you get past the Rotating Gear area, there's a high-tech tunnel called the Underpass. Look carefully as you keep left and you might spot the Red Door.

The North Lever and the Inner Sanctum

The last and perhaps most important section of the Underground in Blue Prince is the Inner Sanctum. Upon arriving at the location, you should see a lever. Pulling it opens the northern door of the Antechamber, giving you access to Room 46.

Note that, in future runs, the northern door and all other Antechamber doors will be closed again. This means you need to pull the North Lever if you wish to return to Room 46. Don't worry, though, since there are other levers/paths to the Antechamber.

Finally, the eight doors surrounding the lever might have piqued your interest. These are the Inner Sanctum doorways, which are locked by default. You can only enter these once you have Sanctum Keys. So, if you thought your adventures in Blue Prince are over, well, guess again. This is probably one of the most surreal and expansive New Game Plus or post-campaign modes in gaming.