I meant that it's not just a simple moat, it has a meaning 😁
"With walls nearly half a mile long on each side, Angkor Wat grandly portrays the Hindu cosmology, with the central towers representing Mount Meru, home of the gods; the outer walls, the mountains enclosing the world; and the moat, the oceans beyond"

about the safety - well, I think it's about as safe as any popular tourist place in South East Asia - you just have to not leave your belongings unattented probably. I can't think of any dangers that a tourist should be aware of there :)