Croghan Hill is the remains of an extinct volcano of the Carboniferous period and rises from the Bog of Allen in the midlands of Ireland in County Offaly. Though only high it commands extensive views of the surrounding midland counties, across the flat, low-lying expanse of the Bog of Allen. The village of Croghan is located on the southern slope of the hill.Historical associationsThe mound at the summit is thought to be a Bronze Age burial place. It is believed that a Bishop MacCaille had his church there and lived around the time of St Patrick in the fifth century. The area also has strong associations with St. Bridget, who is said to have been born near Croghan hill. In pre-Christian times, Brigid as Brig, Bree or Bri was also associated with the Hill, and the inside believed to be a magic underworld called Bri Ele. Seen from Uisnech, the pointed summit coincides with the midwinter sunrise.The O'Connors of Offaly, the old Gaelic rulers before colonisation and plantation in the sixteenth century, had one of their main residences here, and it was also the place of inauguration of their chiefs. Just north of the hill is a holy well dedicated to St. Patrick (signposted). The late Frank Mitchell, the celebrated geologist, preferred to give the distinction of the "navel of Ireland" not to the hill of Uisneach ( north-east of Athlone) but to the isolated hill, Croghan, which he described as a mass of volcanic rock. While accepting that Croghan Hill was not at the geographical centre of Ireland, Mitchell chose Croghan Hill because it lies in the heartland of the great raised bogs of the midlands. The cooling towers of at least four peat-fired generating stations (when they were operational) could be seen from the summit.