However, the bunker is filled with strange mysteries. The people inside have lost all connection to the world before they entered. They don't know what disaster befell the outside, or why people die immediately if they go through the airlock. They don't know when it will be safe to go outside. They aren't even sure what AD year it is, or how long they've been inside, as the Silo population marks time in "years after the rebellion". And their lives are dominated by weird unexplained rules found in a book called the Pact, rules like it being illegal to create elevators, so they have to schlep up and down 144 levels of a mile deep cylinder via a giant spiral staircase. Other rules include a ban on magnification beyond a certain level, and keeping any objects from the "before times" - which are called relics and destroyed on being discovered.

The show (and book series on which it's based) follows the inhabitants of Silo 18 as they try to figure out the mystery of their own existence.

It's pretty good, probably the first mystery box show I've seen where they actually answer questions at roughly the same rate they raise them. The show is four seasons, all already produced, and no more, so you do have confidence that the show knows where it's going and the story will have a satisfying end.

The website is showing a rough mockup of the silo with the different locations seen in the show, but be warned if you haven't watched it - the website is designed for show viewers and there are spoilers in the text.

The scale of the silo is pretty cool to see, though.