There is one very special type of urban space that is park yet not-park, bounded yet unbound. It depends on an osmotic membrane, which draws people in instead of keeping them out. As urban designers are seriously infatuated with this type of space, there have been endless tiffs and tribulations. So little has their essence been appreciated, they are named simply as The Place, Plaz, Plaza, or Piazza, depending upon which European language you are speaking. Where a Place just grows, it often succeeds. Where urban planners make a forced marriage between a people and a Place, they usually fail. The Places they plan do not attract those gay crowds of smartly dressed fun-loving folk who appear in the slick sketches that persuade clients to implement such schemes. This has led to great anguish, to a little research, and to a few worthwhile conclusions.
Camillo Sitte launched our modern debate on Places (Sitte, 1938). As an architect, he took the problem to be geometrical. Systematic studies of the old squares of Europe led him to conclude that the main factors behind a Good Place were plan, section and layout. Plans, he believed, should be irregular but enclosed. The typical size of "the great squares of the old cities' was found to be 155 mby 63 m (465 ft by 190 ft). Christopher Alexander accepted that such large spaces could work in great cities but argued that most squares should have a diameter of about 20 m (60 ft). Otherwise "they look good on drawings; but in real life they end up desolate and dead' (Alexander, 1977). In cross-section, Sitte believed the width should be equal to the height of the principal building, while the length should be no more than twice this dimension. In layout, Sitte took it as a cardinal principle that statues should be placed on the edges of Places, never in the centres which, as Vitruvius said, should be left for gladiators.
Americans have long admired the squares of old Europe. In making comparable spaces they have had a few great successes, like New York's Paley Park, and many great disappointments. Jane Jacobs considered four squares in Philadelphia, with similar dimensions and at similar distances from the City Hall (Jacobs, 1962). Yet only one of them was "beloved and successful'. Why? If urban designers do not have an answer to this question, they should be debarred from the design of urban squares. Jacobs' explanation was that the one popular space, Rittenhouse Square, was surrounded by diverse land uses, which generate a diversity of open space uses. Of the others, she saw one as a traffic island, one as a Skid Row Park and one as a Pervert Park. While respecting her judgement, I believe that urban outcasts also need space.
William H. Whyte made an extremely thorough study of Plaza use in New York City, using time lapse photography (Whyte, 1980). Like Jacobs, he saw that some Plazas were very popular and most were empty. Why? He found that "what attracts people most... is other people'. If a Plaza has a good relationship with a busy street, people will sit there to watch other people. There should be at least 1000 people per hour walking by at noon. Once they are in the Plaza, "people sit most where there are most places to sit'. They like a wide choice of benches, steps, chairs, low walls, pool edges and planters. They also like a fringe of shops and fast-food outlets. None of these factors, it should be noted, bears any relation to dimensions, cross-sections or the placing of statues. Plaza planning is more difficult than Plaza design, yet both are important. The space must be bounded yet unbound. Success depends on the exact character of the bounding membrane.
Piazza Navona, Rome