Watch: Muslims circle the Kaaba at start of annual Hajj pilgrimage

Saudi Arabia started hosting the annual hajj pilgrimage on Sunday, with over 2 million Muslim faithful ready to take part in the ultraconservative kingdom.

Since their arrival, many people have been seen circling the cube-shaped Kaaba in Mecca, Islam's holiest site.  

The Kaaba represents the metaphorical house of God and the oneness of God in Islam.

Observant Muslims around the world face toward the Kaaba during their five daily prayers.

The pilgrimage represents one of the five pillars of Islam and is required of all able-bodied Muslims once in their life.

In recent weeks, the faithful have arrived in Mecca from across the world, all chanting "Labayk Allahuma Labayk," or "Here I am, God, answering your call. Here I am."

Men attending the hajj dress in only terrycloth, seamless white garments meant to represent unity among Muslims and equality before God.

Women wear loose clothing, cover their hair and forgo makeup and nail polish to achieve a state of humility and spiritual purity.

The hajj offers pilgrims an opportunity to feel closer to God amid the Muslim world's many challenges, including the threat of extremists in the Mideast after the Islamic State group was beaten back in Iraq and Syria and the plight of Myanmar's Muslim Rohingya minority.