Pamela, safe as compared to what? So many factors apply (as in any investment) as to its viability and safety. Certainly owning a commercial shopping building is safer than owning an equivalent amount of Enron stock. But, if that building is financed 125%, it may not be as safe as that stock either. Miss a payment and it belongs to someone else.
As far as saftey from terrorist attack, four buildigs (actually only two......the Murrah Building in OKC was taken out, and the WTC was attacked twice.....once that did damage and once that took the towers out) attacked by terrorists/combatants in the hundred and fifty years since the Civil War indicates a pretty good safety record. I think building in general are more at risk from fire, infestation, flood, or vandalism than from terrorisim (although it could be said.....and at some point WILL be said that vandalism and the gang activity it indicates IS a form of terrorism).
The nice thing about real estate, is control. You have the ability to drive by and see it. You can tell the tenants they must move. You can adjust the rent according to the price index. You can raze it and build something else. You can leave it to heirs or to the humane society and they can do all o fthe above.
Overall, real estate is the safest investment available. The market will determine the return on investment capacity, but under normal circumstances, if you own it (unmargined) it will provide you with a decent income and will not be subject to inept accounting or overseas competition.