Béal na Fir Bhearnan [O’Brienscastle] castle
is a large square partly ruined and lies about ten miles north of Six
Mile Bridge. It is also called Caisleán Bhriain. I have
not been able to make any enquiry about the derivation of Fir Bhearna.
From 
Letters
on the Antiquities of County Clare, 1835 by Eugene O’Curry
Description
in Ordnance Survey
Letters by J. O’Donovan and E. Curry, 1839
Search the online photographic collection for images of O'Brien's Castle
On 1842 Ordnance Survey Map (using GenMaps)
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On 1842 Ordnance Survey Map (via MapBrowser)
