Urdd Gobaith Cymru is to begin a £6.5m project to develop its outdoor centres.
The youth organisation will mark the start of the work at a house formerly used by the head of the Glan-llyn centre near Bala in Gwynedd.
The extended house will become a new stand-alone centre, combining accommodation and teaching spaces.
The 18-month project also includes a new water sport centre at Glan-llyn, and modernisation of parts of the Llangrannog centre in Ceredigion.
Urdd chief executive Siân Lewis said it was "the start of a significant and important project for the Urdd".
"More than 50% of all Welsh schools attend Urdd centres on residential courses, and of those who visited over the past three years, 26% came from the 20% most deprived communities in Wales," she said.
The Urdd said there were 47,000 annual visitors to Llangrannog and Glan-llyn, generating a turnover of £5m.
It is anticipated the increase in visitors at the centres will result in an additional £1.3m in turnover for the Urdd and an increase in staff numbers.
The investment combines a grant from the Welsh Government and match funding by the Urdd.