From Sydney Harbour Bridge to the Eiffel Tower, some of the world’s most iconic buildings will be going dark this Saturday for Earth Hour – the world’s biggest celebration of our planet.

This year’s event takes place at 8.30pm on Saturday March 29, with millions of people around the world expected to join in.

And buildings across Wales will also be taking part in the event - including these 10 landmarks.

The WWF campaign supports "One Planet Wales" - a scheme to encourage people in Wales to use only the nation's fair share of the earth's resources.

1. Castell Coch, Tongwynlais, Cardiff

Like something out of a fairy tale, this Victorian castle overlooks the capital from its stunning location on a wooded hillside. Castell Coch (‘red castle’) was created by William Burgess for his paymaster, John Patrick Crichton-Stuart, the 3rd marquess of Bute, as a rural retreat to complement the opulence of his main residence, Cardiff Castle.

2. Tintern Abbey, Monmouthshire

Set near the river Wye in a stunning wooded valley that inspired William Wordsworth, Tintern was only the second Cistercian foundation in Britain, and the first in Wales. The present-day remains are a mixture of building works from between 1131 and 1536. Little remains of the first buildings but visitors can admire the vast windows and later decorative details

3. Caerphilly Castle

The largest castle in Wales, this fortress has been a great TV and film backdrop, such as for the popular BBC TV series Merlin. Surrounded by moats and watery islands, the castle was built with a concentric ‘walls within walls’ system of defence, containing large and comfortable rooms to live in.

4. National Library of Wales, Aberystwyth

One of the great libraries of the world, and home of many of our nation’s treasures, the library stands proudly above the seaside town of Aberystwyth, offering splendid views of Cardigan Bay.Home to some of Wales’ most historically and culturally important treasures, the National Library of Wales contains millions of books, thousands of manuscripts and archives as well as maps, pictures and photographs, films and music.

5. IKEA Wales, Cardiff

One of many businesses to support Earth Hour, Ikea Wales recently celebrated its tenth anniversary at its location in Cardiff Bay.

6. Caernarfon Castle

One of the most impressive historic buildings in Wales, Edward I’s fortress at Caernarfon features polygonal towers and has easy access to the sea. It had previously been the location of a Norman motte and bailey castle and before that a Roman fort stood nearby.

7. The Senedd, Cardiff

The Senedd officially opened on St David’s Day in 2006 on the waterfront of Cardiff Bay. It is home to the National Assembly for Wales’ Siambr (debating chamber) and Committee Rooms. Fittingly for Earth Hour, the building includes a number of eco-friendly features to reduce energy use and save water.

8. Sherman Cymru Theatre

Following a major revamp in 2012, Sherman Cymru Theatre reopened in Cardiff city centre with two auditoria, a new rehearsal room and an impressive new façade. The finished theatre includes low energy lighting and natural ventilation to reduce the building’s carbon footprint.

9. St David’s Hotel, Cardiff

This five star hotel on the waterfront in Cardiff Bay is well known for its striking ‘sail’ roof design. The building incorporates a glass-backed atrium from floor to ceiling, giving a vision of space and natural light.

10. Cardiff Central Library

Opened by the Manic Street Preachers in 2009, the library on the Hayes is one of the capital’s most sustainable as well most iconic buildings. The glass and concrete structure is designed to maximise natural light and retain heat. Its grass roof also helps remove CO2 and other pollutants from the air in the city centre.