September 3, 2018
#2041: Frontiers explain

[In a single framed picture a hand drawn rhomboid is shown. At the inside a few small arrows pointing to the four sides. The text in the middle reads:]
Human achievement so far
[Text above the top left side:]
Space
[Text above the top right side:]
The oceans
[Text below the bottom left side:]
The human mind
[Text below the bottom right side:]
Alaska
[Caption below the frame:]
Final remaining “frontiers,” according to popular usage