"The mechanism for operating the Pneumatic Dispatch is of the simplest description. A tube, a car, a revolving fan! Little more is required. ... The pneumatic car, protected from the possibility of accident, will run up mountains, along beds of rivers, and under the streets of cities, when the steam locomotive will as much of a curiosity as the old lumbering stage-coach now is." -- Alfred Ely Beach, "The Pneumatic Dispatch," 1868. Like most of the visionary proposals featured in Irene Cheng and Brett Snyder's new iPhone application "Other Futures," Museum of the Phantom City—described in the quotation above—provides a window into a vision of New York City that never came to pass. The project, developed by multidisciplinary design studio Cheng+Snyder with support from the Van Alen Institute's New York Prize Fellowship, uses mobile technology to "transform the city into a living museum." Over a dark aerial map of the city, diffuse pink dots indicate nearby proposal sites while white dots signify visionary proposals further afield. Stemming from contemporary research into how new technologies can enhance the way people experience the city, the Museum of the Phantom City gives venturesome New Yorkers (with an iPhone) a chance to imagine New York's many possible futures through a series of unrealized visionary projects from the 19th century to today. These "speculative proposals" run the gamut from Beach's 1868 pneumatic subway (a short piece of which was in fact built downtown) to Buckminster Fuller's 1960 proposal for a dome over Midtown Manhattan. With the application, Cheng and Snyder hope that people will envision New York through the dreamer's lens. The result is an overwhelming, interactive "choose your own adventure" book. On the World Trade Center site alone, visitors are enchanted by everything from post-Sept. 11 competition renderings to the monumentally phallic 1908 Hotel Attraction, designed by Catalan architect Antoni Gaudi. Though concentrated in Manhattan, the proposals range in scale from a total re-conceptualization of the city to a lone building or monument. Cheng and Snyder's work entices people (particularly those of the architectural persuasion) to engage with their surroundings using modern digital technology. Rather than limiting one's iPhone to the simple, utilitarian act of finding directions on Google Maps, Other Futures adds an element of wanderlust to the satellite imagery used on a daily basis. In its current incarnation, however, the Museum of the Phantom City has considerable room to grow and improve. Two visionary proposals for the southern tip of Roosevelt Island—Louis Kahn's 1973 proposal for a monument to President Franklin Delano Roosevelt and Zion and Breen's 1960s proposal to place the Temple of Dendur (now at the Metropolitan Museum of Art) on the same site—are emblematic of the application's present limitations. To achieve the pure moment of spontaneous discovery the museum intends to create, one would ideally approach the sight without any notion of its appearance. Given the trek to Roosevelt Island, or other isolated sites, some might prefer to check out the proposals online. And yet, the journey there is as much a part of the Cheng+Snyder project as the tantalizing mirage at its end. No single moment of discovery prevails. The phantom city is all around us. Musings aside, if the application can reach a certain critical mass, in which it encompasses not only decades of visionary proposals by famous architects, but also the unrealized plans of Robert Moses or even historical images, then it may conceivably add an entire new layer of information to the city. New York may at once be imagined as a place of unfinished dreams and vanished memories and as an architectural and historical museum that exalts as much in the present as it does in potential pasts and futures. To the skeptic who has perused the small online images of Cheng+Snyder's Web site and would rather not venture into the museum, go to the tip of Roosevelt Island and conjure Kahn's memorial. Or go to Bryant Park and watch the helicopters land on Raymond Loewy's 1941 airport suspended on steel pylons. For a brief, illusory moment, the phantom city is real and the real city, irrelevant. Now open your eyes, find the next pink dot on your iPhone, and do it all over again.