Adha, a period of "communal enjoyment" for Muslims worldwide, has officially arrived. Here's what we've learned about the Islamic holiday.

The Hajj leading up to Eid al-Adha is one of the five pillars of Islam. The pilgrimage is one of the largest religious gatherings in the world. Mecca, considered the holiest city in Islam, is the site of Muhammad’s first revelation of the Quran.

Less spending, higher prices and fewer animal sacrifices subdued the usual festive mood as the Muslim holiday of Eid al-Adha was celebrated in many parts of the world.