Eid al-Adha is fast approaching (September 1). Ahead of the Holy day, millions of Muslims from all over the world will be embarking on hajj – one of the five pillars of Islam – in Mecca, Saudi Arabia, which begins on the first moon sighting. Mecca, the holiest city in Islam, is the birthplace of the Prophet Muhammad (PBUH), and is home to the largest mosque in the world, The Masjid al-Haram. Nestled in the center of the mosque is the Kaaba, a black, cube-shaped structure, which thousands of worshippers circle during the pilgrimage. From stunning architecture photos to shots of the breathtaking Kaaba, this round-up highlights the beauty of the holy city. Here, discover stunning Mecca photos on Instagram ahead of Eid al-Adha.