And the kings of the earth, and the great men, and the rich men, and the chief captains, and the mighty men, and every bondman, and every free man, hid themselves in the dens and in the rocks of the mountains; And said to the mountains and rocks, Fall on us, and hide us from the face of him that sitteth on the throne, and from the wrath of the Lamb:
- Revelation 6:15-16 (KJV)

The first bunkers were build for the government during WWII, e.g. to protect against a nuclear attack so that the government could continue to govern.

Consider this bunker in Kelvedon Hatch, UK.

The entrance is well hidden:

- By Genesisman26 at English Wikipedia / Wikimedia Commons

This is what the inside looks like:

- By Scott Wylie from UK / Wikimedia Commons / CC BY 2.0

Watch this YouTube video for the full tour.

Modern day "doomsday bunkers" look much more appealing, and are designed way better.

- By Atlast Survival Shelters

Check out this website for more information on bunkers, silos, and panic rooms.

Modern day bunkers are very luxurious. (Think: swimming pool, cinema, etc)

If you can't afford a bunker under your house, why not get a community bunker together with several other families?

And what about those underground cities I hear so much about?

You can also build your own bunker in your backyard of course.

- Source