Why is the ninth month called September?
"magnificent tomb," 1540s, from Latin mausoleum, from Greek Mausoleion, name of the massive marble tomb built 353 B.C.E. at Halicarnassus (Greek city in Asia Minor) for Mausolos, Persian satrap who made himself king of Caria. It was built by his wife (and sister), Artemisia. Counted among the Seven Wonders of the ancient world, it was destroyed by an earthquake in the Middle Ages. General sense of "any stately burial-place" is from c.1600.
A tomb, or a building containing tombs. Mausoleums are often richly decorated. The Taj Mahal is a mausoleum.