Rachel Whiteread, Ghost, National Gallery of Art, Washington. Photo: Adam via Flickr (https://www.flickr.com/photos/slackeronline/758146410/in/photolist-dYt59K-fCEpr-4quHWa-8Lg11o-53cJsi-2228P9i-29ZGvQ-5DicBn-5DicRt-5DnucS-bxRYy-bxNna-dpsUi9-DeQXhp-4uMZqh-58kaW1-251LtRY-21MERhU-27FYDZG-RHxPoJ-npobUg-4XZyi3); CC BY 2.0