Answer:
I have a little pool with two layers of wall around it. One white and soft and the other dark and hard. Amidst a light brown grassy lawn with an outline of a green grass.
I am like thunder in your cranium
I run around the city but I never move.
I can be simple or I can be complex. I can be found in this riddle or in everyday life. I can be shapes or even colors.
What can you catch but not throw?
I am a rock group with four members. All dead one was assassinated.