The annual Hajj pilgrimage is one of the world’s largest religious gatherings, as some 2 million people flock to Mecca, Saudi Arabia, to participate in one of Islam’s five pillars of faith. Every year, the pilgrimage roughly doubles the number of people sharing space in Mecca, a city that’s home to roughly 2 million residents.
The pilgrimage falls between Aug. 30 and Sept. 3 this year, though Muslims from around the world typically begin arriving in Mecca in the days and weeks leading up to the official start date.
It’s considered an obligation for observant Muslims to undertake the pilgrimage to Mecca at least once in their lifetime if they are physically and financially able.
During the pilgrimage, Muslims from all over the world gather together for five days to pray as one community and celebrate the history of their faith. From the Masjid Al Haram, or Grand Mosque, complex to the hills of Mina, the rites include circling the Kaaba seven times and visiting sites of historical and religious importance.
Pilgrims are required to obtain a special Hajj visa and travel with their passport and proof of vaccination. Mansour Al-Turki, a spokesperson for the kingdom’s Interior Ministry, told reporters in a press conference on Tuesday that over 450,000 were turned away for lack of legitimate visas.
Hajj has suffered several major accidents and security issues, including a number of stampedes in recent years that have killed hundreds of pilgrims at a time.
Going into this year’s Hajj, Saudi forces deployed more than 100,000 security forces to ensure the holy event runs smoothly.
In spite of security risks, Hajj offers pilgrims an experience that can be both physically challenging and spiritually fulfilling. As one pilgrim previously described to HuffPost: “Hajj requires extreme effort but then offers extreme beauty, peace and joy in return.”
Scroll down for a peek at this year’s Hajj pilgrimage:
Muslim worshippers, some carrying umbrellas to protect them from the scorching sun, gather for prayer at Namirah mosque near Mount Arafat, also known as Jabal al-Rahmah (Mount of Mercy), where the Prophet Mohammed is believed to have given his final sermon.
Pilgrims are seen gathered on the Mount Arafat.
Pilgrims are seen as they pray on the Mount Arafat, also known as Jabal al-Rahmah (Mount of Mercy).
Muslim pilgrims take a selfie at the Grand Mosque in the holy Saudi city of Mecca.
Muslim worshippers perform the evening (Isha) prayers at the Kaaba, Islam's holiest shrine, at the Grand Mosque in Saudi Arabia's holy city of Mecca.
A Muslim pilgrim reads the Quran in the Saudi holy city of Mecca, on the eve of the Day of Arafat -- the climax of the Hajj pilgrimage.
Muslim pilgrims gather in the holy city of Mecca before heading to Mina for the start of the annual Hajj pilgrimage in Saudi Arabia.
Muslim pilgrims pray at the Grand Mosque in the holy Saudi city of Mecca.
A young girl looks on as Muslim pilgrims pray at the Grand Mosque in the holy Saudi city of Mecca.
Muslim pilgrims sit and circumambulate around the Kaaba, the cubic building at the Grand Mosque.
Muslim worshippers pray outside the Grand Mosque in the holy city of Mecca in Saudi Arabia.
A Muslim man uses his cell phone as pilgrims walk and pray on Mount Arafat, also known as Jabal al-Rahma (Mount of Mercy), southeast of the Saudi holy city of Mecca.
- This article originally appeared on HuffPost.