Crymlyn Bog National Nature Reserve, near Swansea

What's here


Crymlyn Bog is the largest lowland fen in Wales and its extensive reed and sedge beds are home to a wide variety of wetland plants, birds and insects.

The best way to experience this National Nature Reserve is to walk the trails which include boardwalks through the heart of the fen.

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

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

Walking trails

The walking trails are waymarked from start to finish.

Look out for the information panel at the start of the trails.

Find out about walking trail grades.

Bog Walk

  • Grade: easy
  • Distance: 1 mile/1.4 kilometre
  • Time: ¾ hour
  • Trail information: The trail follows level grassy tracks and sections of boardwalk. There are several gates. Please stick to the boardwalks as there is dangerous wet ground. 

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

  • Grade: easy
  • Distance: 1¼ miles/2.21 kilometres
  • Time: 1 hour
  • Trail information: The trail follows level grassy tracks and sections of boardwalk. There are several gates. Please stick to the boardwalks as there is dangerous wet ground.

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.

What to see on the 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.

The landscape and wildlife varies depending on which time of year you visit – here’s what to look out for.

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.

National Nature Reserves in Wales

There are over 70 National Nature Reserves in Wales.

Find out more about National Nature Reserves.

Visiting safely

We want you to return home safely after your visit here.

You are responsible for your own safety as well as the safety of any children and animals with you during your visit.

Please note:

  • Stick to the boardwalk when out on the fen as there is dangerous wet ground.
  • Canal with deep water – stick to the towpath, keep away from the water’s edge and do not swim.
  • The towpath can be muddy in wet weather – wear footwear with a good grip.

For advice and tips to help you plan your visit here go to Visiting our places safely.

Opening times

Please check the top of this webpage for any changes to these opening times.

The car park barrier is locked overnight.

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

Changes to visitor facilities

See the top of this webpage for details of any planned closures or other changes to visitor facilities here.

For your safety, always follow instructions from staff and signs including those for trail diversions or closures.

We may divert or close trails whilst we undertake maintenance work or other operations and we may need to close other visitor facilities temporarily.

In extreme weather, we may close facilities at short notice due to the risk of injury to visitors and staff.

How to get here

The car park for Crymlyn Bog National Nature Reserve is 1 mile from the A483 dual carriageway through Swansea (the Fabian Way).


The postcode is SA1 8LN.

Please note that this postcode may not take you to the car park if you use a sat nav or navigation app.

We suggest you follow the directions below or use the Google map on this page which has a pin on the car park’s location.


Exit M4 at junction 42 onto A483 to Swansea city centre.

Pass Swansea University’s Bay Campus, then turn right at junction for Fabian Way Park and Ride car park.

Turn around here and rejoin the A483 travelling back towards the M4.

Turn left immediately after BMW service garage and by Mile End pub.

Follow this road (Wern Terrace) and turn right at T-junction with Tir John Road.

Follow this narrow lane for ½ mile, bearing left at the civic amenity site, and the car park is on the right.


View this place on the What3Words website.

Ordnance Survey

The Ordnance Survey (OS) grid reference for the car park is SS 685 942 (Explorer Map 165).

Public transport

The nearest mainline railway station is in Swansea.

For details of public transport go to the Traveline Cymru website.


Parking is free of charge.

The car park barrier is locked overnight.

Overnight parking is not permitted.

Contact details

There are no staff at this location.

Contact our customer team for general enquiries during office hours, Monday to Friday.

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Other places in South West Wales

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