Is this an indoor or outdoor display?

There are a bunch of DIY YouTube videos showing how to build a motor driven turntable. Most of them seemed poorly conceived to me, using motors that are too small or not really rated for continuous use, but the videos might inspire a better approach. One relatively easy approach for home builders is using a pulley on the turntable and the motor, connected with a belt. Pulley ratios and motor speed can easily be calculated and you probably have an appropriate motor in your junk box. In any case consider the likelihood of children and pets being caught up in the contraption.