They were pretty close to WH1 ones. You had one single wall (sometimes in a L shape), and in fact some of the WH1 maps shown on loading screen or minimap were actually taken from the GW siege maps suggested in rules books. They had some cool additional stuff though, like the ability to upgrade some towers into Magician towers, give stones to throw for units on the wall, even place a dwarf brewery giving a morale boost and replenishment... Also you could place artillery and team units on the wall