Completed in 1902 for Switzerland's Albula Railway, the Solis Viaduct is a towering masterpiece of stone masonry spanning 42 meters across an 89-meter-deep canyon. Modern concrete bridges rely on steel reinforcement, which suffers catastrophic spalling when water penetrates microscopic cracks, freezes, expands, and corrodes the metal within. The Solis Viaduct, however, contains no internal steel.
Instead, it relies on classical arch physics, local materials, and thermodynamic smarts to withstand more than 120 winters of violent thermal expansion and contraction. The arch's primary defense is continuous, massive compressive stress. Gravity forces the limestone and dolomite stones, known as voussoirs, tightly together, preventing water from easily creeping into load-bearing seams.
Additionally, the masons purposefully avoided rigid modern cements, choosing breathable lime-based mortar instead. Lime mortar acts like a physical and moisture buffer: it is slightly flexible, porous, and softer than the surrounding stone. When liquid water inevitably enters the joints, the lime mortar absorbs the physical shock of ice crystallization and permits moisture to evaporate harmlessly during thaw cycles rather than bursting the rocks apart.
Built-in internal drainage channels also funnel snowmelt away from the structural core, preventing water accumulation altogether. By working with physics rather than fighting it, this unreinforced stone giant effortlessly outlasts modern concrete structures in one of the world's harsher freeze-thaw environments.