High in the hills above the Mediterranean, Israeli troops worked while soldiers from a country still technically at war with them peered down from only metres above.
The odd spectacle played out this week as Israel continued work on a new concrete wall along its northern border with Lebanon. A few Lebanese soldiers watched from a tower just on the other side.
Israel has spent years building barriers to keep out Palestinians from the occupied West Bank and Gaza Strip as well as African migrants crossing from Egypt.
Earlier this year, new construction began along the Lebanese border, where Israel is building a wall equipped with cameras in the hope of thwarting any attempt by its enemy Hezbollah to infiltrate and attack.
It follows up on earlier construction in 2012 of a wall around the Israeli town of Metula next to the Lebanese border.
Israel says all portions of the wall will be on its side of the so-called blue line - the UN-established ceasefire line put in place after its withdrawal from southern Lebanon in 2000.
But Lebanon says some sections will cut into its territory and earlier this year pledged a diplomatic push to prevent construction.
Lebanon's plans to explore for oil and gas offshore in waters eyed by both sides have added to the controversy.
Israeli military officials told journalists during a tour of the work near the Mediterranean coast on Wednesday that the wall, replacing a fence, was being built for defensive purposes.
Israel fought a war with Lebanon-based Shiite militant group Hezbollah in 2006. The border area has remained relatively quiet since.
"This obstacle basically relates to the intentions, the spoken intentions, the threats made public by Hezbollah since 2011, to infiltrate into Israel and to attack Israeli communities south of the blue line," said Major Tomer Gilad.
"We're taking these threats seriously."
NINE METRES HIGH
Israel has so far built 11km of the wall and a budget is in place for two more.
The military hopes to eventually extend it some 130km, stretching the length of the frontier.
If financed in full, work is expected to take two years, said project manager Brigadier General Eran Ofir.
Military officials declined to comment on whether it includes underground components to detect and stop tunnel digging, as are being constructed along the border with the Gaza Strip.
The total cost is expected to be 1.7 billion shekels (US$472 million).
It is designed to be some 9m (30 feet) high including steel mesh on top - similar to the wall that cuts off the West Bank from Israel.
It is made of long concrete blocks, with tubes for technological components protruding.
Israel's military stresses it is closely coordinating the work with the UN peacekeeping force in Lebanon, UNIFIL.
Representatives of the Israeli and Lebanese armies meet roughly once a month, with UNIFIL mediating, to coordinate not only work on the wall but other issues that could lead to misunderstandings or clashes.
Israel and Lebanon have been involved in a series of conflicts over the years and the two remain technically at war.
But the reason for the wall has less to do with the Lebaese army than Hezbollah, an Israeli military official said.
"NOT JUST WHAT YOU'LL SEE"
Tensions run deep between Israel and the Iranian-backed group.
Hezbollah has been preoccupied with other issues in recent years, having sent several thousand of its fighters to back Syrian President Bashar al-Assad in his country's civil war.
It has lost many hundreds of fighters, including senior commanders, since it deployed in Syria, where the war is now winding down.
But from Israel's point of view, it has gained as well by learning new tactics while fighting alongside Iranian and Russian troops, who are also backing Assad.
Israel's military believes Hezbollah has between 100,000 and 120,000 short-range missiles and rockets, as well as several hundred longer-range missiles.
But the potential for shootings and infiltrations, as well as the need for surveillance, is the reason for the wall, it says.
"It's not just what you'll see, the cement wall," the senior Israeli military official said, adding there were components he could not talk about that make "what we can see from this much, much better."