Nicolas Poussin's most famous painting is?

Nicolas Poussin's most famous painting is "Et in Arcadia Ego," created around 1637-1638. This work depicts shepherds discovering a tomb in an idyllic landscape, prompting reflections on mortality and the passage of time. The painting is celebrated for its classical composition, rich symbolism, and the way it embodies the ideals of the Baroque period. Poussin's influence on the development of French art and the classical tradition is profound, making this painting a significant piece in art history.