A Strategic Link to the Front
The railway section Logatec–Godovič–Črni Vrh represents one of the most intriguing yet least‑known infrastructural undertakings of the First World War. Beneath the area of Naklo in Logatec lie the remains of a 198‑metre‑long railway tunnel, designed for a standard‑gauge line that was intended to connect Logatec with Godovič and further with Črni Vrh. The tunnel runs along an azimuth of 35°, stretching from today’s Pavšičeva Street toward Naklo, and stands as one of the few surviving traces of an ambitious military construction project that history never allowed to be completed.
Logatec — a key logistical hub of the Austro‑Hungarian Army
During the First World War, Logatec served as one of the principal logistical centres of the Austro‑Hungarian military. It was here that supplies, ammunition, equipment, and troops destined for the Isonzo Front were loaded, unloaded, and redistributed. To meet the enormous transport demands, the army constructed a narrow‑gauge military railway (feldbahn) toward Idrija in 1915, threading its way through the rugged karst terrain.
More than 20,000 prisoners of war, mostly Russians, were forced to work on this line. They laboured under harsh conditions—poorly clothed, underfed, and exposed to the elements. Their contribution was essential for maintaining the supply routes that kept the front alive.
Why a standard‑gauge railway?
The narrow‑gauge feldbahn soon proved insufficient. It was too slow and lacked the capacity required by a large army. As a result, military planners proposed a standard‑gauge railway, which would:
• relieve the overstretched road network across Hrušica and Črni Vrh,
• enable faster transport of heavy equipment,
• provide a reliable supply route independent of the Bohinj Railway, which was frequently disrupted by fighting,
• strengthen the logistical backbone of the Isonzo Front.
The most demanding structure on this planned route was the tunnel beneath Naklo, whose construction began in 1916.
Construction of the tunnel — an ambitious project overtaken by events
Work on the tunnel progressed rapidly and involved:
• manual excavation and mechanical drilling into hard limestone,
• construction of retaining walls and embankments,
• excavation of service galleries,
• the combined labour of military engineers and prisoners of war.
By the autumn of 1917, nearly the entire 198‑metre length had been excavated, and the tunnel profile was already partially shaped for the installation of tracks.
A sudden end — the breakthrough at Kobarid
On 24 October 1917, the breakthrough at Kobarid (the Twelfth Isonzo Battle) radically changed the strategic situation. The front line collapsed and shifted far to the west, deep into Italian territory. With the Isonzo Front suddenly relocated, the need for a new supply railway through Logatec vanished overnight. Construction was halted immediately, leaving the tunnel unfinished and unused.
The tunnel beneath Naklo therefore never received its tracks, never saw a locomotive, and never fulfilled its intended purpose.
The tunnel today — a silent monument to wartime engineering
Today, the tunnel stands as:
• a remarkable example of wartime engineering,
• a memorial to the suffering of prisoners of war who built it,
• an open‑air classroom for understanding early 20th‑century construction techniques,
• a rare surviving fragment of a large but unfinished military infrastructure project.
Its authenticity and state of preservation make the Naklo tunnel an important part of Slovenia’s technical and cultural heritage, telling a vivid story of logistical challenges, military urgency, and human endurance during one of the most devastating conflicts in history.