Built in 1929 and demolished in 1930, the Barcelona Pavilion was rebuilt on the original site in 1986. Is it the “same” building? Many architects and critics question the reconstruction’s authenticity, dismissing it as a “fake.” Why the pavilion has inspired such doubt is an important topic because it relates to the very definitions of architecture. What determines a building’s identity—form, function, context, material, or something else? As a historically important work that has existed in more than one instance, the Barcelona Pavilion offers an extraordinary opportunity to consider this question. Examining the distinctions between the two structures highlights conventional standards of critical evaluation, exposing architecture’s core values and interrogating the very concept of preservation.