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Crymlyn Bog National Nature Reserve, near Swansea

The largest lowland fen in Wales

What's here

Dogs welcome
Wildlife hide
Parking (free)
Walking trail

Coronavirus update


The car park and all trails here are open.


Visiting our sites safely


We are working hard to provide a safe and welcoming experience as our sites re-open.


Please take personal responsibility for your safety, making additional preparations ahead of your visit and abiding by the safety measures in place.


We have changed the normal route for some of our trails to help you maintain social distancing – please follow signs on site.


See our tips about how to plan for and enjoy a safe visit.


Crymlyn Bog is one of the most important wetland sites in Europe.

Its survival is remarkable considering its location next to industrialised Swansea.

Over the years, its neighbours have included an oil refinery, power station and rubbish tip, together with numerous coal mines and other industrial works, and yet the bog has remained largely intact.

The best way to experience the reserve is to walk the trails which include boardwalks through the heart of the fen.

Nearby is the slightly smaller National Nature Reserve of Pant y Sais, where there is a short boardwalk accessible for wheelchair users.

Bog or fen?

Bogs are fed solely from rainwater, while fens are also fed by streams and groundwater.

A number of streams feed into the ‘bog’ here, producing a rich habitat much more typical of East Anglia’s fenland than South Wales.

And so, strictly speaking, it should be called Crymlyn Fen.

National Nature Reserve

Crymlyn Bog is a National Nature Reserve.

National Nature Reserves are places with some of the very finest examples of wildlife habitats and geological features.

There are over 70 National Nature Reserves in Wales.

Find out more about National Nature Reserves.

Wildlife highlights

The extensive reed and sedge beds are home to a wide variety of wetland plants, birds and insects.

Reedbeds great for birds

Large numbers of reed warblers and sedge warblers breed here, along with Cetti’s warbler, grasshopper warbler, reed bunting and water rail.

In early summer the reserve is alive with the sound of birdsong as they set up their territories.

Scarcer visitors, normally found in the East Anglian fens, include marsh harrier, bearded tit and the elusive bittern.

You can also see buzzard, kestrel, sparrowhawk and red kite flying over the reserve.

Fantastic fen for bugs

Easiest of all to spot are the numerous dragonflies and damselflies that hover and dart across the bog’s open waters.

Butterflies are plentiful, too, such as the yellow brimstone.

Britain’s largest and rarest spider, the fen raft spider, lives here. It is confined to open water areas and so you are very unlikely to see one during your visit.

Wetland flora

Amongst the reed and sedges, special wetland flowers include yellow iris, marsh cinquefoil and greater spearwort.

Look out for the big clumps of royal fern which is a Crymlyn speciality.

Closures and diversions

Please note:

  • Sometimes we need to close or divert trails for your safety whilst we undertake maintenance work or other operations
  • Occasionally we may have to close a site in extreme weather, such as high winds or snow and ice due to the risk of injury to visitors or staff
  • Please always follow any instructions onsite and make sure you follow any temporary diversion signs in place

Walking trails

Both walking trails are waymarked.

Horses and ponies graze some parts of the trails.

Bog Walk

1 mile, 1.4 kilometre, easy

This walk follows the boardwalks out into the heart of the fen. Listen out for the calls of reedbed birds in early summer and look out for the display of wildflowers in spring and summer.

Bog and Balloons Walk

1¼ miles, 2.21 kilometres, easy

This slightly longer walk also follows the boardwalk but it returns via the ‘Balloon Field’. This was the site of a World War Two barrage balloon to deter German air attacks on the Llandarcy oil refinery – you can still see the circular concrete anchor points set in the ground.

Other routes

The Wales Coast Path passes the edge of the reserve.

There is a public footpath to the top of the adjacent Kilvey Hill opposite the car park.

Opening times

The car park barrier is locked overnight.

The visitor centre is only open for pre-booked visits or events.

How to get here

The car park for Crymlyn Bog is accessed by narrow roads from the Fabian Way (A483 dual carriageway). It is one mile (1.6 kilometres) from the A483.


From Swansea city centre: follow the A483 (Fabian Way) east out of the city centre towards Cardiff. Pass a large retail park and cross over the river. 100 metres after the junction for the Fabian Way Park and Ride, turn left immediately after the BMW service garage and by the Mile End pub. Follow this road (Wern Terrace) and turn right at the T junction with Tir John Road. Follow this narrow lane, bearing left at the entrance to the civic amenity site. After ½ mile, the car park is on the right.

From M4: Exit on Junction 42 onto A483 (Fabian Way) to Swansea city centre. Pass Swansea University’s Bay Campus on the left and then turn right at junction for Fabian Way Park and Ride. Turn around in the Park and Ride and rejoin the A483 travelling east back towards the M4. Turn left after 100m (immediately after the BMW service garage and by the Mile End pub). Follow this road (Wern Terrace) and turn right at the T junction with Tir John Road. Follow this narrow lane, bearing left at the entrance to the civic amenity site. After ½ mile, the car park is on the right.

Ordnance Survey map

Crymlyn Bog is on Ordnance Survey (OS) map 165.

The OS grid reference is SS 685 942.

Public transport

There is a bus service to Port Tennant, about half a mile away.

For details of public transport visit

Find out more

Contact details

Tel: 0300 065 3000


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