This study explores the vertical and horizontal recirculation mechanisms of tropospheric ozone (O3) in Barcelona utilizing WRF-CAMx simulations. We analyzed extreme O3 episodes that occurred in 2015, 2018, and 2019. These episodes significantly impacted public health in one of Spain's most populated urban areas. Key contributing factors include prior O3 accumulation, the weekend effect, Tramontana winds, and multiregional air mass transport. Our findings identified a recirculation mechanism based on the trajectory of polluted air masses. O3-enriched air masses affected the city in the early morning hours after being transported from higher altitudes. These insights enhance the understanding of O3 dynamics and may aid in predicting future pollution episodes in Barcelona and similar complex terrains.