Millions of Muslims from all over the world have converged on Mecca in Saudi Arabia to partake in Islam's annual Hajj pilgrimage.

Muslims from around the world travel to participate in the Hajj each year, an annual sacred pilgrimage to the holy city of Mecca in Saudi Arabia. The big picture: The deeply spiritual journey, which every able-bodied and financially capable Muslim is expected to undertake at least once,

Hajj 2025 will occur June 4-9, guided by lunar cycles, but there are other astronomical alignments you need to know about around the world's largest annual pilgrimage.