Vandals are believed to have used a chainsaw to cut through wooden railings and "hack down" threatened tree species at a protected geothermal landmark at Rotorua.
Police are investigating the damage done to restoration work around the Waiotapu Hot and Cold Pools on Saturday night.
Banks and vegetation at the popular pools have been damaged in the past and the Department of Conservation project has put up barriers to isolate areas that needed to be restored.
Over the weekend vandals cut through wooden railings, including one at a bridge, and destroyed 10 prostrate kanuka trees, a nationally threatened species.
"It is a privilege to have a place as special as the Hot and Cold Pools and it is heartbreaking to see the land and the hard work that has gone into protecting that land treated with such disrespect," environmental liaison officer Evelyn Forrest said.
"These projects are part of the iwi plan to protect and restore natural and cultural values to our lands.
"It is needless vandalism and those responsible need to be held to account."