Imagine the most extreme urban environment on earth?a place three times as dense as Manhattan, enveloped in a constant flow of water, beset by a relentless stream of rural migrants, plagued by annual monsoons, and threatened by climate change. A place where the very earth beneath your feet is constantly shifting from dry to wet, where categories like “dry” and “wet” in fact mean very little, since most of what exists is somewhere in between. This is Dhaka, capital city of Bangladesh. Home to 14 million. Since 2007, architects Stephen Kieran and James Timberlake have directed a design-research laboratory on Dhaka for graduate students at the University of Pennsylvania School of Design. What began as a desire to help a city in need became an immersion in investigating its ebbs and flows, mapping its urban systems, and charting its development via annual visits. The result of this extended study is Alluvium: Dhaka, Bangladesh, in the Crossroads of Water, a cross-genre book that incorporates diverse media and layers of narrative and analysis to encourage new readings and perspectives. The book includes first-person narratives by architects and planners, documentary photographs, and maps and infographics that visually represent the intricate connections between people, water, land, and health in this delta megacity.