Sweetheart Abbey, or Dulce Cor, as the monks referred to it, was founded in 1273 by Lady Devorgilla in memory of her husband John Balliol who had died in 1268. So devoted was she to her late spouse that she carried his embalmed heart around with her in an ivory and silver casket. After her death she was buried in the abbey church with her husband's heart buried beside her. Some might find this gruesome, others an enduring tribute to the power of love!
There's more about Sweetheart Abbey on the Undiscovered Scotland site.