A massive structure stretching two miles in length holds the distinction of being known as the world’s longest building. The Klystron Gallery at SLAC National Accelerator Laboratory in Menlo Park, California, spans an impressive 3,073 meters (1.9 miles) and takes approximately 35 to 40 minutes to traverse on foot at a moderate pace. This colossal facility, visible even from space, was constructed as a crucial component of the Stanford Linear Accelerator project, aiming to unravel the mysteries of matter by colliding particles.
The construction of the SLAC project, which began in the 1960s, incurred costs of about $114 million, with an additional $18 million allocated for research and development, totaling around $132 million (£98 million). Adjusted for inflation, this amount translates to over $1 billion in today’s currency. The heart of the site, the Klystron Gallery, serves as a massive industrial hub supporting a two-mile underground particle accelerator, featuring rows of klystrons – highly potent microwave amplifiers essential for accelerating electrons to near light speed within the underground tunnel.
This extensive gallery resembles an endless industrial corridor, housing machinery, electronics cabinets, and service areas that extend far into the distance, creating a surreal perspective in photographs. The underground accelerator beneath the gallery stands out as one of the most meticulously engineered straight objects ever built, necessitating consideration of the Earth’s curvature during alignment to maintain precision across the vast distance.
Established in 1962, SLAC, initially Stanford Linear Accelerator Center and later SLAC National Accelerator Laboratory, is overseen by Stanford University on behalf of the U.S. Department of Energy. Today, it stands as a prominent global hub for various scientific disciplines including particle physics, X-ray science, astrophysics, and materials science. Noteworthy research conducted at SLAC has contributed to multiple Nobel Prize-winning discoveries, with sections of the original accelerator now powering the Linac Coherent Light Source, a cutting-edge X-ray laser.
The Klystron Gallery, widely recognized as one of the longest modern structures globally, remains a significant feat of engineering. While debates persist on what constitutes the “world’s longest building,” the Klystron Gallery’s unique purpose as a scientific support structure separates it from conventional buildings like airports or shopping malls. Its sheer length, comparable to 30 football fields placed end to end, makes it an iconic feature visible across the Californian landscape, serving as a testament to human ingenuity in unraveling the mysteries of the universe.