Pods, Planes, Pickups

Elon Musk has executed some crazy ideas over the years.

The South Africa-born entrepreneur co-founded PayPal in 1998 and sold the online-payments service to EBay four years later for $1.5 billion. He also helped start the electric-car company Tesla Motors, which has a market value of about $18 billion, and the rocket maker Space Exploration Technologies. He runs both of those companies and is also the chairman of SolarCity, one of the biggest providers of solar power systems in the U.S.

Despite his accomplishments, Musk isn't ready to fly his spaceship off to a quiet planet somewhere and retire just yet. Instead, he's talked about his next grand visions, such as making electric planes, developing a new mode of transportation and constructing an entire city -- on Mars. Given that he has enough ideas to last several lifetimes, the 42-year-old billionaire might want to add "eternal life" to his list of projects.

Here's a look at some of the ambitious plans and dreams swirling inside the mind of Musk. We'll wait and see which ones become reality.