The area around Għajn Tuffieħa Tower has been closed off to the public due to significant safety risks, the police said on Monday.
The site is popular for hikers and provides one of the most beautiful views in Malta.
But concerns were raised over the years about the state of the cliff.
"The structure and surrounding area are at risk of collapsing, making it dangerous to access," the police said as they urged people to stay away.
Times of Malta had reported, back in 2007, that the historic coastal tower, built by the knights in 1637, was in danger of collapse because the cliff face was retreating.
The tower itself was damaged in a storm in February 2023, suffering a gaping hole at the top of the structure. That damage was repaired.
Photographer and amateur historian Conrad Neil Gatt raised his concerns about the tower's safety five months ago on social media. Speaking to Times of Malta, he said he visited the site a month ago, where he found the gate to the tower open due to the wind. " This was very dangerous. Going through the gate meant that the people risked the tower possibly falling on them." He said that scaffolding around the tower had been there for at least a year and had started to rust. He had contacted the Lands Authority and the Superintendence of Cultural Heritage but they brushed his concerns off, he said.
Rock structures on either side of the headland where the tower is located in the north west of Malta have been eroding and collapsing over the years.
Landslides have occurred on the clay slopes overlooking the beach known as il-Qarraba near Ġnejna.
In 2023 a large boulder crashed into Popeye Village at Anchor Bay.
Last year part of Fomm ir-Riħ bay was closed off because of a rockfall and the danger of further collapses, exactly a year after an architect's warning on Times of Malta.