Which Martian crater did NASA's Spirit rover explore?

NASA's Spirit rover explored Gusev Crater on Mars. Spirit landed there on January 4, 2004, as one of NASA's two Mars Exploration Rovers, arriving three weeks before its twin, Opportunity.

Gusev Crater was selected because orbital images suggested it might once have held a lake. Spirit initially investigated broad volcanic plains and found mostly basaltic rocks, rather than the extensive lake sediments scientists had hoped to see. The rover later climbed into the Columbia Hills, where it found rocks altered by small amounts of ancient water.

Spirit operated for more than six Earth years. It became stuck in soft soil in 2009 and sent its final communication in March 2010. Gusev is often confused with Meridiani Planum, which was Opportunity's landing region, or Jezero Crater, explored much later by Perseverance.