There's a lot more to Twmbarlwm than great exercise. From ancient burials to fortifications to monks, it's all happened on these green slopes.

Long before 21st century sightseers braved the challenge of its steep sides, Twmbarlwm was shaped by a variety of ancient hands.

The modelled hump on its high, exposed peak is unmistakably the work of a lingering human presence.

However, an exact record of Twmbarlwm's past, and the people who visited it remains a mystery.

Chris Morgan, Caerphilly CBC heritage and museums officer, said: "The first evidence of this is the Bronze Age (2100BC to 700BC) cairn. This tomb would have probably initially contained a single burial, although it may well have been reused."

However, as the hollowed top implies its contents have been robbed, this grave keeps its secrets.

The summit's magnificent view over the surrounding country, with the Bristol Channel to the south, would have made it an excellent location for defence. This would very likely have attracted the Silures during the Iron Age (700BC to 43AD),

Chris said: "They appear to have encircled its summit with a rampart and ditch. This was probably crowned by a timber palisade. Whether this incorporated an Iron Age village is not known."

Interest in the site didn't end here, as it appears to have been used during the Norman Conquest.

Chris said: "The hill fort's defences appear to have been incorporated into a motte and bailey castle. This motte was a large mound of earth and can still be seen in the eastern corner today."

Although the Normans mostly built them, Chris says the Welsh were known to have used them too, so the original architects are a mystery. A timber-built keep would probably have topped the motte, and the bailey seems to have followed the shape of the earlier fort. Like others built all over Britain at this time, this would have housed livestock, provisions and possibly soldiers.

However Twmbarlwm's bailey differs from the usual pattern, Chris reveals. "Oddly, this encircling rampart and ditch is not complete and there are several gaps along its southern and eastern side."

These mysteries are not easy to solve and there are no definite answers, with the real truth obscured through over 4,000 years of human use.

This isn't necessarily a negative, though. When they reach the top, with its stunning view, walkers can enjoy the mystery as well as a hard-earned rest.

A future collaboration between Caerphilly CBC, the Forestry Commission and Cadw will see an interpretation plan for Twmbarlwm established, so that people can learn more about the area's rich history.

This will probably be housed in the new visitors centre, reveals Rowena Riley, life long learning officer for Caerphilly Museums and Heritage. "This may take the form of living archeology, where archeologists try to create things the Silures would have used, looking at their warrior side, such as the use of chariots, weaving and spears. There may also be more formal archeology such as geophysics," she said.

While the site is well known for its ancient earthworks, many local people will be surprised to learn that Twmbarlwm was also home to a Cistercian monastery.

Known as Cefn Rhyswg, it was founded by in the late 1170s by Hywel ab Iorwerth, and linked to Llantarnam. Uniquely it was the only monastery to be founded by a Welsh ruler. The monastery continued until their dissolution by Henry V111 in 1536.

For more historical information on the site, contact Rowena on 01495 235877