"Tiberias Municipality contractors were baffled, as all the concrete they poured into the 20-meter (65 feet) deep foundation holes they had drilled before building a new neighborhood disappeared. Suddenly, as a mechanical digger exposed a cave entrance, they found their missing concrete — and a unique 2,000-year-old burial cave." Source: Archaeology News Network.
Note: Archaeologists have been finding ancient tombs and underground passages in Israel for decades. For instance, see this 2015 story about a tomb discovered in the Judean foothills and this 2007 story about an ancient tunnel discovered near Jerusalem's Old City.