3 image fixed (inlining HTTP images doesn't work anymore); for more info, see https://gist.github.com/Glorfindel83/9d954d34385d2ac2597bbe864466259f
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I believe many did.
Hopewell (mound builders) : This Hopewell mound in Newark Ohio looks an awe-full lot like a circular wall with a gate in the upper left hand corner.
Hopewell mound

regarding the Inca, these look like defensive walls to me. inca ruins http://www.rontravel.com/Web_Photos_Happy_Cannibal/K_South_America/Peru_Cuzco_Sacsayhuaman_Vista.jpginca ruins

I believe many did.
Hopewell (mound builders) : This Hopewell mound in Newark Ohio looks an awe-full lot like a circular wall with a gate in the upper left hand corner.
Hopewell mound

regarding the Inca, these look like defensive walls to me. inca ruins http://www.rontravel.com/Web_Photos_Happy_Cannibal/K_South_America/Peru_Cuzco_Sacsayhuaman_Vista.jpg

I believe many did.
Hopewell (mound builders) : This Hopewell mound in Newark Ohio looks an awe-full lot like a circular wall with a gate in the upper left hand corner.
Hopewell mound

regarding the Inca, these look like defensive walls to me. inca ruins

2 replaced http://1.bp.blogspot.com/ with https://1.bp.blogspot.com/
source | link

I believe many did.
Hopewell (mound builders) : This Hopewell mound in Newark Ohio looks an awe-full lot like a circular wall with a gate in the upper left hand corner.
Hopewell mound http://1.bp.blogspot.com/-1TZSrLi9iks/T1Nl4UtuuoI/AAAAAAAAAuw/o9IAOuPUNtc/s1600/Great%2BCircle%2B1.jpgHopewell mound

regarding the Inca, these look like defensive walls to me. inca ruins http://www.rontravel.com/Web_Photos_Happy_Cannibal/K_South_America/Peru_Cuzco_Sacsayhuaman_Vista.jpg

I believe many did.
Hopewell (mound builders) : This Hopewell mound in Newark Ohio looks an awe-full lot like a circular wall with a gate in the upper left hand corner.
Hopewell mound http://1.bp.blogspot.com/-1TZSrLi9iks/T1Nl4UtuuoI/AAAAAAAAAuw/o9IAOuPUNtc/s1600/Great%2BCircle%2B1.jpg

regarding the Inca, these look like defensive walls to me. inca ruins http://www.rontravel.com/Web_Photos_Happy_Cannibal/K_South_America/Peru_Cuzco_Sacsayhuaman_Vista.jpg

I believe many did.
Hopewell (mound builders) : This Hopewell mound in Newark Ohio looks an awe-full lot like a circular wall with a gate in the upper left hand corner.
Hopewell mound

regarding the Inca, these look like defensive walls to me. inca ruins http://www.rontravel.com/Web_Photos_Happy_Cannibal/K_South_America/Peru_Cuzco_Sacsayhuaman_Vista.jpg

1
source | link

I believe many did.
Hopewell (mound builders) : This Hopewell mound in Newark Ohio looks an awe-full lot like a circular wall with a gate in the upper left hand corner.
Hopewell mound http://1.bp.blogspot.com/-1TZSrLi9iks/T1Nl4UtuuoI/AAAAAAAAAuw/o9IAOuPUNtc/s1600/Great%2BCircle%2B1.jpg

regarding the Inca, these look like defensive walls to me. inca ruins http://www.rontravel.com/Web_Photos_Happy_Cannibal/K_South_America/Peru_Cuzco_Sacsayhuaman_Vista.jpg