Polnagollum (pronounced Pol-na-GOLL-um) is a stream-passage cave in County Clare, Ireland. It is a dwelling place of fairies and spirits, a threshold where the world above meets the hidden world below. Like many such places in Irish tradition, Polnagollum is less a site to explore than one to respect, an opening where a careless step or a lingering glance might draw you across the veil.