Authorities are urging visitors to the Giant’s Causeway in Northern Ireland to stop tossing coins between the rocks, warning that the volcanic stone columns (made of basalt) at the popular site are being damaged.

According to the National Trust, which manages the UNESCO World Heritage Site, the tradition is causing structural harm to the rocks. Over time, coins rust and expand to three times their original thickness, placing immense pressure on the stones and leading to cracking.

“We urge people to stop this practice and leave no trace, so this natural wonder can remain special for future generations,” said Cliff Henry, a representative of the National Trust, on Wednesday.

In 2024 alone, the Giant’s Causeway drew over 648,000 visitors, reinforcing its status as one of Northern Ireland’s most visited landmarks.

Henry explained that “Coins rust and expand, tripling in thickness, which puts huge stress on the rocks and causes them to crack.” He also noted the unsightly residue left behind by oxidized metals like copper, nickel, and iron where coins corrode.

To tackle the issue, the National Trust brought in stone conservation experts who have removed coins from ten different areas of the site. The full restoration effort is expected to eventually cover the entire site and is estimated to cost around £30,000.

New signage will also be installed, encouraging visitors to “keep your coins in your pockets.”