Situated approximately 3km from Newbridge, Pollardstown Fen is the largest remaining spring-fed fen in Ireland and is a very important site nationally and internationally.

Pollardstown Fen is a post-glacial fen which began to develop approximately 10000 years ago when a large lake covered the area. Over time, this lake became filled with dead vegetation, accumulating and eventually turning into fen peat. The calcium-rich water found here prevented the usual change from fen to raised bog and continues to prevent this process today.

The fen is largely composed of reedbeds, freshwater pools, patches of scrubland, and a large woodland area which lies at the western end of the reserve.

Its location is of international importance, as this type of system is now rare in Ireland and Western Europe. In addition, it contains a number of rare vegetation types and invertebrates, along with an uninterrupted pollen record of the changes in the composition of its vegetation going back to the last ice age.

Many rare plant species exist in the area such as Shining Sickle Moss and the rare arctic-alpine moss Homalothecium Nitens. Other rare plant species include Narrow-leaved Marsh Orchid Slender Sedge and Marsh Helleborine.

Many resident bird species and also winter and summer migrants can be found in the habitat. Among them are regular breeders such as Mallard, Teal, Cood, Snipe, Sedge Warbler, Grasshopper Warbler and Whinchat. Other species such as Merlin, Marsh, Harrier and Peregrine Falcon occur regularly as vagrants.

Managed by the National Parks & Wildlife Service, parking is available at the site and interpretive signage will guide visitors around the boardwalk route.