What's an example of a paradox

Penrose triangle is a famous example, as I read from a long book about paradoxes.

Answer: One of the most famous paradoxes is called the liar's paradox, and is evident in the following sentence: "This statement is false." Another variation of the liar's paradox would be, "Everything I say is a lie."

Explanation: Paradox is a seemingly absurd or self-contradictory statement or proposition that when investigated or explained may prove to be well founded or true