"A Frog at the bottom of a well" (井底之蛙) is a common Chinese idiom or phrase used to describe a person with limited outlook. Here is the (translated) folktale about the origin of the phrase.
A frog lived at the bottom of a well. One day, he saw a big sea turtle at the side of the well.
"What a good time I'm having, living here in this well," the frog told the turtle. "When I'm in a good mood, I can hop along its coping and I can go back for a rest by a crevice in the bricks when I get tired. I can swim for fun with only my head and mouth above water, or stroll through the soft mud to my delight. The crabs and tadpoles all envy me for I'm master of this well where I can do whatever I like. Why don't you come in and see for yourself what a nice place this is?"
The turtle accepted the invitation. But before he could get one foot into the well, his other one got caught on something.
He stopped, stepped back and then began to describe the sea to the frog. "Have you ever seen a sea?" he asked. "It's tens of thousands of miles wide, and thousands of feet deep. There were floods in ancient times nine years out of ten, yet the sea's water never overran it's banks.
Later, there were droughts seven years out of eight, yet the seawater never shrank much. This is because no floods or droughts can do much with the sea. It's really wonderful to live in it."
Hearing this, the frog fell silent, staring at the turtle in disbelief.
Moral: Some people refuse to know beyond their own world.
—By Zhuang Zi (369-286 BCE)