Mark Thornton makes an interesting case that the building of large skyscrapers is a good indicator of an over-inflated economy ready to crash:
The skyscraper index, created by economist Andrew Lawrence shows a correlation between the construction of the world's tallest building and the business cycle. Is this just a coincidence, or perhaps do skyscrapers cause business cycles? A theoretical foundation of "Cantillon effects" for the skyscraper index is provided here showing how the basic components of skyscraper construction such as technology are related to key theoretical concepts in economics such as the structure of production. The findings, empirical and theoretical, suggest that the business-cycle theory of the Austrian School of economics has much to contribute to our understanding of business cycles, particularly severe ones.
Read the rest, or listen to the MP3, or listen to the author interviewed by Lew Rockwell.