Offa's Dyke erosion repaired with 400 tonnes of stones
4 February 2014 Last updated at 20:20 GMT
More than 400 tonnes of crushed stone will be flown by helicopter to the Brecon Beacons to restore an eroded footpath on Offa's Dyke.
Brecon Beacons National Park Authority will fly in the material to Hay Bluff which is 677m (2,220ft) above sea level over the next five days.
The stone will help improve more than two miles (3km) of path.
Charlotte Dubenskij reports.