This paper takes stock of megaproject management, an emerging and hugely costly field of study, by first answering the question of how large megaprojects are by measuring them in the units of mega, giga, and tera, and concluding with how we are presently entering a new “tera era” of trillion-dollar projects. Second, total global megaproject spending is assessed, at US$6 to US$9 trillion annually, or 8% of the total global gross domestic product (GDP), which denotes the biggest investment boom in human history. Third, four “sublimes”—political, technological, economic, and aesthetic—are identified and used to explain the increased size and frequency of megaprojects. Fourth, the “iron law of megaprojects” is laid out and documented: Over budget, over time, over and over again. Moreover, the “break–fix model” of megaproject management is introduced as an explanation of the iron law. Fifth, Albert O. Hirschman’s theory of the “Hiding Hand” is revisited and critiqued as unfounded and corrupting for megaproject thinking in both the academy and policy. Sixth, it is shown how megaprojects are systematically subject to “survival of the unfittest,” which explains why the worst projects get built rather than the best. Finally, it is argued that the conventional way of managing megaprojects has reached a “tension point,” in which tradition is being challenged and reform is emerging.