Oldest active construction project

The currently active construction project that has been going for the longest time is the Sagrada Familia in Barcelona, Spain. This Art Nouveau basilica was designed by noted Spanish architect Antoni Gaudi. Construction commenced on 19 March 1882 and is still ongoing as of 4 November 2024, some 142 years 230 days later. The structure of the building is expected to be finished in 2026, and the project fully completed in the early 2030s.

Gaudi envisioned the construction of the Sagrada Familia as a centuries-long project, akin to the great cathedrals of medieval Europe. When asked about his schedule, he famously remarked "My client is not in a hurry". The pace of construction has accelerated dramatically over the last few decades, as wooden scaffolding and workers with chisels and hammers have given way to tower cranes, computer models, and precisely CNC machined stonework.