It would be a lot easier if you were in a helicopter above the city. We're trapped inside our galaxy, so it's hard for us to make the map. The Milky Way is a mostly flat disk with a spiral structure. The Milky Way contains over 100 billion stars. All the stars in the galaxy are moving.
Gravity causes the stars to move in orbits, the gravitational pull from all the other stars.
The orbit's all go around the galaxy's center in giant ellipses. Our sun makes a near-circular orbit every 240 million years. But the mass we see is not as much as the gravitational pull indicates. There seems to be more mass than that we can see. Astronomers work this out by making a rotation curve .