The Old City of Akko, but you get the sense that it is not always the most well organized part of the city.

why a lot of gas bottles are visible for all in Israel ? It can really be dangerous.

Should be safe. in fact safer then mains gas. I have used them for many years without incident . the problem is if you do not follow safety procedures . Turn them off when not in use. The smell from any leaks is quite strong . I believe a chemical component is added to them so that leak detection is easy. When the bottled gas gets to a level to cause such a huge explosion the smell would be overpowering to residents