Standing at Arafat (Arafah Maidan) on the Day of Arafat (9th Dhul-Hijjah) is the most essential rite of Hajj - without it, Hajj is incomplete. While Tawaf (circumambulating Kaaba) and other rituals are important, the Arafat standing is the core requirement. Praying in Mecca and visiting Medina are not Hajj-specific requirements.