Porth yr Ogof facts for kids

The main river entrance to Porth yr Ogof cave

Porth yr Ogof is a famous cave found near the village of Ystradfellte in Wales. It sits close to the southern edge of the Brecon Beacons National Park. The cave is part of the Afon Mellte river system. The name 'Afon Mellte' means 'lightning river,' probably because its water levels can change very quickly after rainfall.

In 1998, the cave's underground passages were measured to be over 2.25 kilometers (about 1.4 miles) long. Porth yr Ogof has fifteen entrances. One of these is the largest cave entrance in all of Wales, and one of the biggest in the entire United Kingdom! It stands nearly 20 meters (65 feet) wide and 8 meters (26 feet) high. Many years ago, Porth yr Ogof was a 'show cave' where visitors could explore. However, it's not as decorated or beautiful as other caves like Dan yr Ogof. Because of this, it is now mostly used to teach people how to explore caves safely.

Exploring Porth yr Ogof's Features

Most people enter Porth yr Ogof through its wide main entrance. You can either use a dry path on the left side or walk through the river, which is usually knee-deep. Another popular way to enter is through an opening called the Workman's or Tradesman's Entrance. From here, a passage on the left leads to a muddy area inside the cave.

Challenging Passages Inside

Inside Porth yr Ogof, you'll find some interesting and challenging spots:

• The Wormhole: This is a curving, narrow tunnel that you have to crawl through. It's located on the right wall of the main entrance.
• The Letterbox: This is a rectangular, tight space within one of the passages.
• The Creek: This feature is found deeper inside the cave.
• The Washing Machine: There are actually two spots called "The Washing Machine." Both of these areas have large amounts of water.

Porth yr Ogof is no longer a commercial tourist attraction. Instead, it serves as an important training cave for people learning about caving. There are two short potholes that are easy for beginners to explore. The cave is generally quite wet.

Water Features and Sumps

One notable water feature is the White Horse Pool. It gets its name from a white mineral deposit on the back wall that looks like a horse. Even though the edges of this pool are shallow, the water in the middle is several meters deep.

The cave also has many sumps. A sump is a section of a cave passage that is completely filled with water, meaning you would have to dive through it. Most of these sumps are found in the parts of the cave north of the Tradesman's Entrance.

History and Geology of the Cave

The name 'Porth yr Ogof' comes from the Welsh language and means 'gateway to the cave.' This cave is located in the valley of the Afon Mellte. It lies within a relatively narrow band of Carboniferous Limestone, which is a type of rock that caves often form in. Usually, except after heavy rain, the riverbed downstream from Ystradfellte is dry. The river only reappears on the surface just before it enters Porth yr Ogof.

Humans have known about Porth yr Ogof for many centuries. However, because the cave passages can flood very badly, no evidence of people living there in ancient times has been found. The cave and its many visible fossils were written about by Edward Lhuyd, a famous Welsh naturalist, in his writings. Later, in the 1800s, the first people to explore caves also mentioned Porth yr Ogof.

Images for kids

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  Porth yr Ogof resurgence in flood conditions