Explanation

They could see the laborers pointing to the hills,

their gestures indicating something of interest or significance in the distance.

The preposition "at" has several common uses:

Location: Used to indicate a specific point or place.

The party is at John's house.

Time: Used to indicate a specific time or moment.

They arrived at dawn.

Direction or Aim: Used to indicate a direction or goal.

He threw the ball at the target.

Group or Event: Used to indicate attendance or participation in a group or event.

He is good at sports.