Walk 2: Underground rivers & dry canal

Limestone is a relatively soluble rock. Water trickling through cracks in limestone gradually enlarges them into underground passages and caves. The only natural drainage from Lough Mask is through such caves in the Carboniferous limestone. The many springs around Cong are where much of the water draining out of Mask re-emerges at the surface to flow the short distance into Corrib. Human attempts to produce a surface drainage from Mask to Corrib, the famine-time canal cut, failed because the water simply drains into the cavities in the rock. However, the excavations provide abundant material in which to find fossils of coral and other animals from the Carboniferous tropical sea.

"The Risings" at Cong

Park in Cong and walk to the bridge at the north end of the village. Large volumes of water issue from springs on both sides of the road and flow to the east and west to meet again at the abbey and encircle the village. Walk through the village to the abbey and (after your archaeological investigations) cross the footbridge to the Ashford Castle woods. Turn right (signed Pigeon Hole) and walk along the riverside. In the winter several small springs issue from the pathside. The river rapidly diminishes and its source is soon met at a group of springs in a natural limestone amphitheatre. Continue through the tunnel under the road and follow the woodland walk to the Pigeon Hole cave (about 15 mins), where 61 steps descend to an underground river passage. This may be dry in summer but in winter water flows past, briefly glimpsing sunlight before continuing to rise at Cong. The Pigeon Hole can also be reached by road [GR 133 554]. A guide to other caves in the area, with notes on local history, can be found in "The Glory of Cong" by J.A. Fahy, available locally. Return to Cong.

Return to Cong. At the south end of the village the road bridge crosses both the river, which has flowed the short distance from the springs, and the dry canal. A footpath leads to cuttings for an intended lock system (now blighted by a derelict handball court). It is possible to walk north along the canal cutting for a short way, beside which are small but well-formed limestone pavements with deep grykes (fissures enlarged by dissolving of the rock).

Limestone pavement

Drive to Carrownagower Bridge [GR 146 589] and park carefully off the narrow road. The bridge spans the man-made canal, which may or may not have water in it depending on the time of year! In summer almost all the flow out of Lough Mask is underground and any surface drainage along the canal may have sunk into the ground before reaching this far. Walk along the track on the east side of the canal to the piles of excavated rock. A rummage among these can yield good specimens of columnar colonial corals that lived 340 million years ago.