Complex sentence: It is of such a width that it is impossible to stand upon one shore and view the other side, and it encircles the main city like a ribbon, being both a moat against intruders and the lifeline of the people in times of peace.
Split into simpler sentences: It is of such a width that it is impossible to stand upon one shore and view the other side. It also encircles the main city like a ribbon, being both a moat against intruders and the lifeline of the people in times of peace.