Inisheer (also called "Inis Oirr") is the smallest of the three Aran Islands, off the coast of Galway, Ireland. Before I went I was told by an Irish friend that it has a spiritual quality to it and it does: the quiet (that you can literally feel), the sparseness (I only saw a few people while there) and the island's raw beauty meant you could truly unplug from modern life.
Its size means you can easily walk it in a few hours. Besides O'Brien's Castle ruins, you'll find a gentle landscape of homes painted in soft colors (dotting only one side of the island), endless stone walls and a cemetary filled with ancient Celtic crosses. I look forward to returning.