Then maybe you've come across a Futuro House!
(photo copyright: Peter Dowden)
In 1968, Finnish architect Matti Suuronen concieved and built a futuristic home out of fiberglass. It was a modular design, capable of being carried to the home site easily by truck or even by helicopter. It contained a large room divided by plastic partitions into a small kitchen, bathroom and bedroom. The entrance was by steps leading up from the base through a hatch, much like a 1950's flying saucer on TV.
There were about 96 of them built, according to the website http://futurohouse.com/ . An estimated 60 of them survive.
I have actually seen one of these in person; there used to be one about 15 miles from where I live now. It was back in the woods on a pedestal (like a flying saucer treehouse) and I have since tried to find it and couldn't. But tonight if the weather is decent I will drive by the site again and take a look, and try to get a photo.