In 2 point perspective there are 2 vanishing points. Quite natural effects can be obtained by assuming that all vertical lines in a drawing are actually vertical, and therefor don’t converge, but that all horizontal lines converge to the ‘horizon’. In perspective the horizon is a theoretical one that is actually your eye level. All horizontals below your eye level converge up, and all horizontals above your eye converge down to the eye level. The discovery in the Renaissance that the vanishing point is at eye level was one of the great turning points in art history.