They have traveled to Karbala from different parts of Iraq as well as other countries.
The holy shrines of Imam Hussein (AS) and Hazrat Abbas (AS) and the area between the two mausoleum known as Bain al-Haramain, have been decorated with lights and banners on the auspicious occasion, which falls on Wednesday, March 8.
Meanwhile, the Governorate of Karbala declared Wednesday a public holiday in the governorate on this occasion.
The 15th day of the lunar Hijri month of Shaaban, known as Nimeh Shaaban, marks the birthday of Imam Zaman (may God hasten his glad advent).
Every year, millions of Shia Muslims around the world hold festivities to honor the event.
According to Islamic teachings, Imam Zaman (AS) is the prophesied redeemer, who will revive peace, administer justice and rid the world of evil.
The following aerial photos show the holy city of Karbala on the eve of Nimeh Shaaban.