A fossil forest in Brymbo, near Wrexham, which pre-dates dinosaurs, has been designated a Site of Special Scientific Interest by Natural Resources Wales.
The site covers an area nearly half the size of a football pitch and contains a variety of 300 million year old fossilised plants and trees.
Natural Resources Wales (NRW) says it is a world class site for plant fossils.
They are the remains of plants which grew in hot, humid conditions near the equator - and include 20 fossilised giant clubmosses that look like massive tree stumps.
The fossils were first revealed in 2004 on the former iron and steel works site in Brymbo. Much of the fossil forest remains buried for its own protection.
NRW says plans are underway, led by Brymbo Heritage Group, to establish an excavation and visitor centre on the site that will ensure the right conditions to study and display the fragile fossils.
In the meantime, Brymbo Heritage Group organises guided tours, open days and community digs for people to see the fossil forest and industrial heritage.
Some of the best and rarest fossils have been removed and are being conserved in the National Museum of Wales. They will be returned to Brymbo for public display, once a suitable building is ready.
It is illegal to remove fossils or damage a Site of Special Scientific Interest.