Oriel y Parc has received funding from the EU's Objective 1 scheme
A £3.5m landscape gallery and visitor centre featuring works by Picasso, Lowry and Rembrandt has opened its doors in St David's in Pembrokeshire.
First Minister Rhodri Morgan launched Oriel y Parc, described as one of the most eco-friendly buildings in Wales.
King Letsie III of Lesotho will also visit as part of a state tour of Wales.
A Pembrokeshire National Park Authority and National Museum Wales partnership, it also includes a cafe, artist studio, education centre and discovery room.
It will feature treasures from the museum's collections.
Works by Graham Sutherland, famous for his Pembrokeshire landscapes, will form a permanent part of the gallery's rolling exhibitions.
Pieces by Pembrokeshire artist Alison Hayes - the only artwork to be displayed that is not part of the national collection - will also be shown in the gallery, capturing life on both Skomer and Grassholm islands.
Simon Hancock, chairman of the park authority, said: "What we have developed here in St David's is a first-class facility which we hope will inspire people to go out and discover the unique landscape of their national park for themselves."
The building received £1.6m of EU Objective 1 funding.
National Museum president Paul Loveluck said: "Oriel y Parc provides us with a wonderful opportunity to reach out to new audiences and enables many more people to be able to access and enjoy the exciting collections held by National Museum Wales."
The centre harnesses green technologies including a ground source heat pump, a rainwater harvesting system, sedum and turf roofs, photovoltaic roof cells and solar panels.
King Letsie III of Lesotho is on his first state visit to Wales.
He is in Wales for four days to see the work of Dolen Cymru, an organisation that promotes friendship and understanding between Wales and Lesotho and raises funds for charity projects in the southern Africa country.