‘London’s megaproject ecology’ describes some of the infrastructure megaprojects recently undertaken in London to illustrate some of the different ways of organizing projects. These include the Jubilee Line extension, High-Speed 1, the new fifth terminal at Heathrow, the Crossrail project, and London 2012 Olympics. It is important to understand the context within which projects are initiated and unfold over time. It raises many questions that cannot be answered by project management’s traditional preoccupation with the ‘lonely project’, such as: How do individuals, teams, and organizations involved in projects learn from the past? How do they develop their knowledge and prepare for the future? Four broad categories of project organizing are identified: single-project organizations, project-based organizations, project networks, and project ecologies.