okay its been a while but here is the next concept map:

the map is called "A City Divided" it is a blue zone city surrounded by zone walls. an earthquake struck splitting it in two and making a path for a fast flowing river of bright green sludge. the river has such high concentrations of tiberium that tiberium and tiberium glaciers have grown along the edge of it. the city was evacuted. recently GDI has put a pair of service bridges across the chasm. as shown by the light gray lines. tiberium is shown as pink and the tiberium "glaciers" are purple. the chasm can't be crossed except at the two bridges or with aircraft. the only ways down into the chasm are indicated as red squares. although it appears otherwise from the map you can go anywhere inside the brown areas of the chasm by going down into it and the entire chasm floor is covered in tiberium.
the only ways to get around are to go through the city, the brown areas on the left and right edges are rough terrain and are impassible. the only ways into the city are through the tan holes indicated. zone walls are indestructable by conventional weapons but will fall if hit by a superweapon. the black squares in the city are buildings, the ones closest to the chasm would be damaged or destroyed. the outer ring road of the city is a double street with trees between the lanes, beyond that is a forested area before the zone walls. the blue areas are ponds but could also be blue tiberium if the designer wanted that instead, i personally feel that this map has enough tiberium without it. the pale blue squares are tiberium spikes. the dark gray areas are roads and the red X's are player start locations.