Brain teaser: The earth is underground but the name is... in the sky?

Sounds absurd but extremely reasonable, only those who are observant can find the answer to this tricky riddle.

This question seems easy but is incredibly difficult: "What kind of soil is underground but appears in the sky?". Sounds absurd, right? Soil must be underground, how can it be up in the sky? However, that is the beauty and richness of the Vietnamese language. Some people immediately think of natural phenomena, others think of a special type of soil. What do you think?

Brain teaser: The earth is underground but the name is… in the sky?

Leave your answers in the comments section and check out the answers of your "competitors".

Khanh Son

Source: https://vtcnews.vn/cau-do-hack-nao-dat-nam-duoi-dat-nhung-ten-nam-tren-troi-ar990917.html