What does the asteroid belt look like?

Short answer: You can't really see it at all. Asteroids are so spread out that it just looks like the rest of space.

Long answer: In science fiction, asteroid belts are often shown as areas of space densely packed with rocky asteroids like this...

Fictional Asteroid Belt

In reality, asteroids aren't anywhere near this close to each other. Although there are millions of asteroids, they are spread across so much space that you can fly straight through without worrying about hitting any. If you were standing on an asteroid you probably couldn’t see any others—they’d be too far away.

In our Solar System we have one main asteroid belt between the orbits of Mars and Jupiter. The largest asteroid, also classified as a dwarf planet, is Ceres with a diameter of 940 km. Asteroids range in size down to tiny particles. There may be up to 1.7 million asteroids with a diameter of 1 km or more in this asteroid belt.

Numerous robotic space probes have flown through our asteroid belt without coming close to any of the asteroids. The chance of an accidental collision is less than one in a billion.