A bunch of architects want to build a $26 billion underwater city in Tokyo - take a look

Earth as we know it might not last forever.

If sea level rise triggers flooding in our cities, if climate change makes it impossible to grow food for billions of people, or if there's some other as-yet unthinkable apocalyptic disaster, humans will need a new home.

The architects at Shimizu Corporation, a Tokyo-based firm, want to build underwater cities that they call Ocean Spirals.

There are no concrete plans to construct an Ocean Spiral, which project leader Masaki Takeuch estimates would cost $26 billion. But the renderings are certainly fantastical.

Check them out below.