Al-Masjid al-Haram, Mecca, Saudi Arabia (US$100 billion)
The pilgrimage to the holy city (a rite known as the
hajj) is the reason why millions of Muslims from around the world make the trip over to Al-Masjid al-Haram. The original “Great Mosque of Mecca” was first built in the 638 CE, and has undergone major renovations over the ensuing millennia. The price tag of the latest
expansion is reported to be US$100 billion, crowning it as the most expensive building in the world, by far.