Heh, that picture brings back memories - especially the section near the back. I had a chance to walk along the Great Wall back in the 90s. It takes some doing to get up those steeper slopes (especially with vendors trying to hawk postcards and other trinkets every 10 yards). It’s a good reminder, though, of what can be done with determination and effort (the Great Wall, not my walking on it!)
Jeb is (once again) entirely wrong.
You don’t have to have fencing on every mile of the border for walls/fencing to be effective. Barriers along the most heavily trafficked routes will cut those routes off, reducing the flow of illegal aliens. Fencing and walls can also be used to create choke points, forcing the Coyote traffickers into narrow access points where border agents can more easily intercept them. That’s a tactic that’s worked for thousands of years.
I also disagree that it would have to cost a trillion dollars or whatever other hooey his pitching. If securing fencing ended up costing $10 million per mile, which would be an astoundingly high figure, then 2000 miles of fencing (and we wouldn’t need that much) would run around $20 billion, if my math is correct. Still a bargain compared to what illegal immigration is costing. I’d even argue we could add things like manned outposts and expanding the fleet of off-road vehicles to cover the rugged areas without approaching anything like the numbers Jeb is spouting.