Sports stadiums, in addition to being costly propositions rarely built with private money, are urban planning killjoys. They're huge, usually in relatively well-used areas, necessitate large amounts of parking, and use a lot of land around the edges for landscaping. They choke off all street life in the immediate vicinity – though the place might be packed in the evenings for games, during the rest of the day, it just takes of the most valuable resource a city has: space. I thought about all of this when I saw the blueprints for London's 2012 Olympic stadiums. They're beautiful pieces of architecture, for sure, but they create these huge voids, and take up what could be very valuable real estate.