Details about the Hamas tunnel system, long considered a major threat to the Israeli military, are being released that show the structures were more complex and advanced than had been believed. 

One of the tunnels, according to information released by the military and documented through photos and video, was located under a hospital and was almost three football fields long, while another was wide enough to allow a car to be driven inside by a Hamas official, The New York Times reported.

Another, reached through a spiral staircase hidden under the house of a senior Hamas commander, was shown to be about seven stories deep, the military's evidence shows. 

Israeli officials and soldiers, along with former American officials, say the tunnels and the machines used to build them came as a surprise.

The tunnel network was believed to be an estimated 250 miles long in December, but since then, the Israeli military believes there are even more tunnels, stretching to between 350 and 400 miles under Gaza, which at its longest area is only 25 miles long.

Further, two officials said there could be up to 5,700 shafts leading to the tunnels. 

There are different estimates about the full scope of the network, but experts say Israeli intelligence and defense failed to understand the importance and extent of the system.

Last January, a top Israeli defense official dismissed the idea that the tunnels could be important in a future war, saying Israel's military strength would prevail. 

But former CIA officer Aaron Greenstone, who has extensive experience in the Middle East told the Times that "Hamas has used the time and resources over the last 15 years to turn Gaza into a fortress."

Hamas which does not have the resources to fight a conventional war, uses the tunnel system as its military bases and to move forces underground while protecting commanders. 

Documents show millions have been spent, with one document from 2022 showing Hamas had budgeted $1 million on doors, underground workshops, and more in Khan Younis, southern Gaza's largest city.

In another report, dating back to 2015, Hamas was shown to have spent more than $3 million on tunnels in the Gaza Strip including under civilian infrastructure, schools, and hospitals. 

There are two kinds of tunnels, the ones for commanders and others for operatives. The commander tunnels are built to be more comfortable to allow for longer stays and sometimes include ceramic tiles, with the tunnels for operatives being smaller and usually more shallow. 

The Israeli military has also obtained lists of families that have tunnel entrances in their private homes.

Meanwhile, destroying the Hamas tunnels has not been easy, according to one official, as they must be checked for hostages and must be made irreparable, not merely damaged. The official said it might take several years to disable the network.

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