By the end of the 18th century, most of Mayfair was built on with upper-class housing; unlike some nearby areas of London, it has never lost its affluent status. The decline of the British aristocracy in the early 20th century led to the area becoming more commercial, with many houses converted into offices for corporate headquarters and various embassies. Mayfair retains a substantial quantity of high-end residential property, upmarket shops and restaurants, and luxury hotels along Piccadilly and Park Lane. Its prestigious status has been commemorated by being the most expensive property square on the London "Monopoly" board.