By far, what is the most expensive building ever constructed?

The world’s most expensive building ever constructed is the Great Mosque of Mecca located in Mecca, Saudi Arabia, with a total construction cost of $100 billion.

The Great Mosque of Mecca is one of the oldest mosques in the world and was built over the course of centuries, starting in the year 638. It has undergone major renovations and expansions over time, the most recent of which was in 2020, and afterward, it officially held the title of the largest mosque in the world in addition to being the most expensive building in the world.