In Norse folklore, both the Acorn and its bearer, the oak tree, bring good fortune. The Vikings associated oak trees with Thor, the god who created thunder and lightning with his great anvil and hammer. Because the tree attracted lightning, it was sacred to Thor. Thus they believed that the Acorn, the fruit of the oak tree, was always spared the God's wrath, and so they began putting a lone Acorn on their windowsills to protect their homes from lightning's wrath.
Sjöfn (pronounced SYO-fn) is the Norse Goddess of Harmony in Marriage. She is one of Frigg’s handmaidens, and it is her job to turn the minds of humans to thoughts of love and passion. She also ensures happy marriages by stopping fights. Sjöfn’s name, which means “affection,” is also seen as Vjöfn or Sjofna.
Brú na Bóinne, County Meath (Ireland). 'Looking at once ancient and yet eerily futuristic, Newgrange’s immense, round, white stone walls topped by a grass dome is one of the most extraordinary sights you’ll ever see. Part of the vast Neolithic necropolis Brú na Bóinne (the Boyne Palace), it contains Ireland’s finest Stone Age passage tomb, predating the Pyramids by some six centuries.' http://www.lonelyplanet.com/ireland/county-meath/bru-na-boinne