Opening a Door

I went for a walk the other day, normal route along the beach, just checking for interesting stuff that might have washed up in the tide overnight, when I found a door, a solid wooden door with a brass door knob, laying flat in the smooth damp sand. I thought the knob might be worth something, and reached down to grab the hardware, when the door opened at my touch, snapped up on the side like it had hinges or something, revealing stairs leading down under the sand. At least, from my perspective it looked like the stair led down. As far as I know, they might have been leading up once I crossed the threshold. Dark stairs that led, somewhere, toward a distant light, I mean, how could I resist, right?