The 24 meter high and 244 meter long railroad viaduct, which spans the village and the Frieda valley from afar, is the landmark of Lengenfeld unterm Stein.

The history of the railroad line itself is impressive. The rail link on which the railroad viaduct was located stretched 805 km from Berlin to Metz in France, which became part of the German Empire after the Franco-Prussian War (1870/1871). In order to reach Metz more quickly from the German capital, some new lines were built and existing lines were extended. As this was done for military reasons, it was given the unofficial nickname Kanonenbahn.

The construction of the Lengenfeld viaduct on the newly created Leinefelde-Treysa section of the line began in 1875. The extensive construction work, which was completed in August 1879, was quite difficult at times due to the rocky and hilly terrain. On September 8, 1879, the first train carrying sand crossed the railroad bridge. A full train crossed the Lengenfeld viaduct for the last time at the end of 1992.

As part of the disused Eichsfeld Cannon Railway, the Lengenfeld railroad viaduct is now used for tourism and can be ridden on bicycle trolleys.