I've discovered some of the earlier works of Paul Murdoch, who designed the controversial Crescent of Embrace memorial for Flight 93.

Apparently he likes working with Red Maple trees... (see extended entry)...

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Here's his "Mushroom of Compassion" memorial in Hiroshima:

and his "Oven of Friendship" memorial near Auschwitz:

As with "Crescent", these memorials are "not about offering explanation for what happened, but to allow people to come to terms with it."