Which zone is defined as a public zone where all players can see the cards' faces?

The zone defined as a public zone where all players can see the cards' faces is the battlefield. In this zone, creatures, artifacts, enchantments, planeswalkers, and any other permanents are all openly visible to all players, allowing for strategic planning and gameplay decisions based on this information.

In contrast, the library, hand, and graveyard are private zones. The library consists of the cards that players have not yet drawn and is not visible to opponents. The hand is where players keep the cards they have drawn and is also private, meaning the cards in a player’s hand cannot be seen by the opponent. Lastly, the graveyard contains cards that have been put there from play or as a result of effects, and this zone too is not public in terms of card visibility, even though players are generally aware of what has been placed there during the game.

This distinction is key in understanding how visibility influences gameplay dynamics and strategy.