We describe a rare case of persistent atrial fibrillation originating from the prominent Eustachian ridge. A detailed mapping using the Advisor™ HD Grid catheter enabled precise identification of the non-pulmonary vein foci at the prominent Eustachian ridge. A local interatrial conduction block was observed during a single ectopy or short run. Highly localized radiofrequency ablation could completely cure persistent atrial fibrillation.