If one has ever been to Israel, looked at an aerial photo, of the land beside the Palestinian territory, you would see a wall in most areas as terrorists shoot through fences at Jews and/or non-Muslims.
The land there is certainly more rocky and rough than along our Southern Border.
Anyone claiming that "a wall can't be built," is saying "I don't want a wall to be built!"
Furthermore, anyone claiming "it would be way too expensive to build a fence," is admitting that money claimed that was set aside in 2006 and partial fences constructed under President Bush and Congress but never seriously intending on building anything, only tricking voters to think that our "leaders" planned on building any kind of barrier; and that person would also by lying about claiming that the expense of a wall would be cost prohibitive, and way less than we spend on illegal aliens (and their Anchor Babies) now, plus Earned Income Tax "Credits" to illegal aliens each and every year and on into the future so far as it exists!
The “anchor babies” tend to be from Asian mothers who may spend as much as $50,000 to come in on a visa, give birth here and go back home with dual citizenship for their baby. So 20 years later they can send their “American” baby to a US university, and who knows what plans the Chinese government might have with regard to sleepers.