How do you make a secret bunker?

How do you make a secret bunker?
How to Build an Underground Bunker in 9 Steps

Get Permission. The most important thing to do is to get the proper permits.
Choose the Location.
Develop a Blueprint.
Pick the Right Bunker Building Material.
Choose the Right Excavating Equipment.
Acquire Key Living Materials.
Start Digging.
Reinforce the Shelter.

How to Build an Underground Bunker in 9 Steps
  1. Get Permission. The most important thing to do is to get the proper permits.
  2. Choose the Location.
  3. Develop a Blueprint.
  4. Pick the Right Bunker Building Material.
  5. Choose the Right Excavating Equipment.
  6. Acquire Key Living Materials.
  7. Start Digging.
  8. Reinforce the Shelter.