To unlock The Challenge in Geometry Dash, you have to use the Vault of Secrets and have enough diamonds.

Quick Scoop: How to unlock The Challenge

  • The Challenge is a secret level hidden in the Vault of Secrets.
  • You unlock it by typing a specific code and having 200 diamonds.

Step-by-step guide (2.1 / 2.2)

  1. Open the main game (paid Geometry Dash).
    • This works in the main Geometry Dash app, not just Geometry Dash Lite.
  1. Go to the Vault of Secrets.
    • From the main menu, tap the gear icon, then the little lock icon at the top right (that’s the Vault of Secrets).
 * If it’s locked, you usually need around **10 user coins** to open it first.
  1. Type the code.

    • In the Vault’s text box, type:
      the challenge

    • After entering this, the secret level The Challenge will appear in the list on the right side.

  1. Meet the diamond requirement.
    • To actually play The Challenge, you must have 200 diamonds.
 * If you don’t, the Keymaster will say something like “You are not prepared. Collect more diamonds.”
  1. Play the level.
    • Once unlocked, you can select The Challenge from the side panel and play it like a normal level.
 * It’s a short, secret level (about 26 seconds long) with a lot of pads, rings, and one spider section.

How to get 200 diamonds faster

  • Beat featured / map pack levels to earn diamonds as rewards.
  • Open chests in the treasure room whenever they’re ready (many give diamonds).
  • Play regularly; diamonds accumulate over time just by progressing in levels and rewards systems.

If the code doesn’t seem to work in 2.2

Some players in 2.2 report that if typing “the challenge” doesn’t show the level, you should:

  • Log into your account in Geometry Dash World first, then go back to Geometry Dash.
  • Re-enter the Vault of Secrets and type “the challenge” again, then save your progress.

TL;DR:
Open Vault of Secrets → type the challenge → make sure you have 200 diamonds → select The Challenge from the side panel and play.

Information gathered from public forums or data available on the internet and portrayed here.