Post a picture please.🙂

Hazard cones, Yellow and black stripes on the stairs, low hanging hazard warning signs, motion activated playback of a voice recording warning of the step ahead, caution sign on a pedestal warning of the step, pressure sensitive device under a rug which will emit the noise a cat makes when stepped on like a whoopee cushion , a gate which only opens when a button is pushed next to a sign on the wall stating a step, and finally a posted doorman or moonlighting Walmart greeter to greet and warn guests about the step.

A change of materials (wood step down to stone floor) plus an obvious handrail usually provides visual clues. I did one project where the long side of the living room was two steps down from the kitchen and breakfast area. (Stupid design from the seventies). We inlaid led lights into the underside of the stair treads to really make them visible.