A three-year project to improve facilities on the bird sanctuary of Skomer island is being officially launched by the first minister.
The Skomer Heritage project has seen accommodation and interpretation centres on the island and mainland refurbished to improve visitor access.
Carwyn Jones is visiting the island on Thursday to see first hand the changes made since the work began.
Skomer is home to thousands of puffins and other sea birds.
Old farm outbuildings on the island have been converted into accommodation for 16 overnight visitors, six volunteers and research staff.
The power for the buildings is all being provided by solar panels and wind turbines.
Skomer and its neighbouring island Skokholm are home to almost half the world's population of Manx shearwater and a significant proportion of the world's grey seals.
'Special part of Wales'
The project has been backed by the Heritage Lottery Fund (HLF), the Tubney Charitable Trust and the Crown Estate.
HLF Wales head Jennifer Stewart said: "The refurbished accommodation and expanded learning facilities has helped encourage more volunteers onto the island and increased the opportunities to develop ecology skills.
"The new multi-media centre has also created fantastic opportunities for students and school children across Wales to get closer to and explore the wildlife on the island."
First Minister Carwyn Jones said ahead of his trip: "The wealth and diversity of wildlife on Skomer has already ensured its place as an area of outstanding natural beauty.
"The sympathetic restoration work carried out as part of this project will only enhance the understanding and enjoyment of visitors to this special part of Wales."
The Wildlife Trust of South and West Wales manages the island on behalf of the Countryside Council for Wales.
There are 6,000 breeding pairs of puffins, 120,000 breeding pairs of Manx shearwater as well as seals and other marine life.