The author on this is not specified, link to the source:
http://designyoutrust.com/sand-castle-by-carla-spagnuolo/
http://shkvarki.org/izobreteniya/item/1296-zamki-iz-peska-kak-iskusstvo-arkhitektury
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From @lindo
The author on this is not specified, link to the source:
http://designyoutrust.com/sand-castle-by-carla-spagnuolo/
http://shkvarki.org/izobreteniya/item/1296-zamki-iz-peska-kak-iskusstvo-arkhitektury