Anti-tunnel barrier along Israel-Gaza Strip border

The anti-tunnel barrier along Israel-Gaza Strip border (sometimes referred to as the smart wall on the Israel-Gaza Strip border) is a smart underground slurry wall constructed by Israel along the entire 40-km length of the Israel-Gaza Strip border to prevent the nationalist militant regime which rules Gaza, Hamas (which Israel, along with other countries regards as a terrorist group) in the Gaza Strip from digging tunnels under the Israel–Gaza barrier into Israel. The project includes excavation to classified depths, and the construction of thick concrete walls combined with alarm devices. 
The new underground anti-tunnel barrier was completed in March 2021. The project had been estimated to cost 3 billion shekels ($833 million). It is located entirely on Israeli land.
Background.
Because of the effectiveness of the Israel–Gaza barrier in stopping infiltration of Israel by Palestinian militants, Hamas adopted a strategy of digging tunnels under the barrier. On 25 June 2006, Palestinians used an 800-metre tunnel dug over a period of months to infiltrate Israel. They attacked a patrolling Israeli armored unit, killed two Israeli soldiers, and captured another one, Gilad Shalit.
Between January and October 2013, three other tunnels were identified – two of which were packed with explosives.
During the 2014 Gaza War, Israel encountered Hamas militants who popped out of tunnels into Israel and attacked soldiers along the border. After the war, Israel located and destroyed 32 tunnels. In 2018, Israel destroyed three new tunnels.
Underground barrier.
The anti-tunnel barrier was constructed in response to the large number of tunnels being dug by the Hamas regime, which could only be of use for infiltration by militants. In mid-2017, Israel began construction of the underground wall several meters in depth. The barrier is equipped with sensors that can detect tunnel construction.
In October 2020, sensors in the underground structure identified a Hamas tunnel. An Israeli military official called the tunnel "The most significant tunnel we have seen to date, both in terms of depth and infrastructure".