Hezbollah spent an estimated $1 billion to $3 billion over the past two decades building an extensive underground military network across Lebanon with assistance from Iran and North Korea, according to a new assessment by Israel's Alma Research and Education Center, which says the full scale of the project has only become apparent since the outbreak of the war in October 2023.

The report argues that Hezbollah's underground infrastructure—dubbed the "Land of Tunnels" by the research center—extends far beyond the cross-border attack tunnels previously revealed by Israel and instead comprises a vast network of strategic, tactical and operational tunnels, along with underground facilities designed to sustain prolonged combat.

The Alma Center first highlighted the scope of the network in an August 2021 report titled Hezbollah's Land of Tunnels – The North Korean and Iranian Connection, which examined what it described as the foreign assistance behind the project.

The latest assessment comes as researchers continue mapping and analyzing the underground system in light of the extensive discoveries made during the current conflict.

From Cross-Border Tunnels to a Vast Underground Network

In December 2018, the Israeli military exposed six cross-border tunnels that extended from Lebanon into Israeli territory.

According to the Israeli military, the tunnels were intended to serve as underground infiltration routes for Hezbollah's elite Radwan Unit in a future offensive into Israel's Galilee region.

Since the war began in October 2023, however, Israeli forces have uncovered what the Alma Center says are much larger portions of Hezbollah's underground infrastructure.

The exposed network includes strategic tunnels located in Hezbollah's principal operational strongholds in southern Lebanon, smuggling tunnels along the Syria-Lebanon border, tactical tunnels spread across the area known as the "Yellow Line" in southern Lebanon, and approach tunnels positioned close to the border contact line.

Researchers also point to the discovery of dedicated underground facilities used for storing weapons, launching rockets and unmanned aerial vehicles, arguing that these installations form an integral part of Hezbollah's broader subterranean network.

The center says it is currently conducting a comprehensive mapping and research project to document the system in greater detail.

Underground Project Built Over Decades

According to the report, Hezbollah spent at least two decades developing the network with technical and engineering assistance from Iran and North Korea.

The project encompasses several categories of underground infrastructure, including strategic tunnels, tactical tunnels, approach tunnels, offensive tunnels and, according to the center's assessment, explosive tunnels designed for future combat scenarios.

Rather than isolated tunnels or individual shafts, the report describes an interconnected and fortified underground defense system extending beneath much of southern Lebanon.

It says extensive networks have been excavated beneath many villages—particularly Shiite communities—consisting of dozens of access shafts, storage depots, living quarters and command posts linked together underground.

Why Researchers Estimate Costs in the Billions

The Alma Center says estimates placing the project's total cost below $1 billion fail to reflect the engineering, geological and logistical realities involved.

Military engineering and underground construction specialists cited in the report estimate Hezbollah invested between $1 billion and $3 billion in its underground infrastructure over the past twenty years.

According to the researchers, several factors explain the enormous expense.

Much of southern Lebanon is composed of hard limestone and dolomite rock, particularly around areas such as the Beaufort Ridge and Ali al-Taher.

Excavating tunnels through such terrain requires heavy drilling equipment, explosives and extensive structural reinforcement using steel supports, wire mesh and sprayed concrete to prevent collapses.

The report argues that even relatively narrow tactical tunnels built to military standards cannot realistically be constructed for only a few hundred thousand dollars.

Drawing on civil engineering benchmarks, the researchers estimate that technically complex tunnels built under these geological conditions generally cost between $2,000 and $5,000 per linear meter, with costs potentially increasing further because excavation had to remain concealed.

Based on those estimates, a single one-kilometer tunnel would cost between $2 million and $5 million simply for excavation and basic structural reinforcement.

Underground Bases Required Advanced Engineering

The report emphasizes that Hezbollah's underground facilities were designed as more than simple passageways.

To sustain dozens of fighters over extended periods while accommodating weapons depots, command centers, living quarters, rocket launch positions and logistical facilities, the tunnels required sophisticated engineering systems.

These included advanced ventilation and air-filtration systems capable of removing carbon dioxide and supplying oxygen to underground chambers.

The facilities also required drainage and groundwater pumping systems to deal with southern Lebanon's karstic limestone formations, which contain numerous underground water cavities, particularly during the winter rainy season.

According to the report, the network also incorporated electrical grids, lighting, encrypted wired communications, backup generators, water supply systems and sewage infrastructure.

The researchers argue that these mechanical, electrical and plumbing systems alone added millions of dollars to the cost of each major underground installation, independent of excavation expenses.

Secrecy Added to the Cost

The report says one of the most expensive aspects of the project was concealing the excavation itself.

Hundreds of thousands of tons of rock removed during construction had to be transported without attracting attention from Israeli surveillance or aerial intelligence.

According to the researchers, the excavated material was likely moved by truck—possibly during nighttime hours—and dispersed across remote valleys and quarries.

Maintaining that level of secrecy, the report argues, imposed logistical costs far beyond those associated with ordinary civil engineering projects.

The Alma Center concludes that the combination of excavation, structural reinforcement, advanced engineering systems and covert logistics makes estimates below the $1 billion-$3 billion range unrealistic, arguing that Hezbollah's underground network represents one of the largest and most expensive clandestine military engineering projects ever undertaken in Lebanon.