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The most famous waterfall on this walk is Sgwd Y Eira, which you can normally walk behind.

Derek and his guide - Tony Ramsey, were scuppered by a rockfall when they did the walk and the path was closed for repairs.

It has now re-opened -

Undeterred, they took in another five beautiful waterfalls on the walk and Tony, a retired professor of geology and Scientific Director of the , showed him some of the fascinating characteristics of the area.

On this walk you will be following the 'farewell rock', the band of sand stone that marks the end of the south Wales coalfield.

When miners reached this rock they knew they had reached the end of the coal reserves and it was time to say farewell and move elsewhere.

Near Pontneddfechan the sand stone, towers above the path, and if you look hard enough you might see some fossils.

The fossils in this rock are plant fossils - approximately 316 million years old and were laid down when Britain was in the tropics.

The first half of the walk follows the river Neddfechan and for just over a kilometre it is a nice easy path that you can push a pram or a wheelchair along, but it can be uneven in places.

The path is a relic of the industrial heritage of this area and is part of an old tramway which used to transport silica rock from mines further up the valley. Silica mining began here in 1822 and you pass some of the abandoned workings along the way.

Silica rock or Dinas rock as it's known in the area was used to make fire bricks. It was used for this purpose because it is made from quartz.

Quartz is an extremely hard mineral with a high melting point, so ideal for lining the walls of furnaces.

The bricks were then exported to America, Europe and Russia, where they are still known as 'Dinas bricks'.

The first waterfall you'll encounter is Sgwd Gwladys. It is formed by water flowing over hard sandstone into a plunge pool below made up of soft mud rock - and after all these years it's still a work in progress.

The rock is continuously eroding (with this particular waterfall, 1.3 metres of rock is eroded approximately every 1000 years).

The next waterfall is the Horseshoe Falls, in the Neath valley, surrounded by oak trees and is quite simply - beautiful.

The next waterfall you'll find is called Sgwd Ddwli Isaf, followed by Sgwd Ddwili Uchaf. As the path climbs higher towards the Pontmelinfach picnic area, the waterfalls get more spectacular.

After an hours ramble through lush tree-lined gorges the terrain starts to change. You emerge from the woodland canopy to find yourself on a hillside before dropping back down the Afon Mellte to the final waterfall on the walk, known as Sgwd Isaf Clun-Gwyn.

At this point Derek hooked up with experienced caving instructor, Gary Evans and they headed underground. This should only be done as part of an organised tour as people have died attempting this on their own in the past.

This is not part of the usual walk - you would normally continue on to the Cwm Porth car park to finish this walk.

The river Mellte disappears underground at Porth Y Ogof, and although it doesn't look that dangerous it poses a threat to cavers - a threat echoed in its name.

Mellte, means 'lightning', because the waterfall levels rise so quickly, so it's something to keep a careful eye on.

Like the rest of the walk, the cave systems have lots more geological interests to explore.

Whether you're under or above ground this walk offers spectacular sights, as well as plenty of water but it goes to show that don't need sunshine to go walking in Wales.

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