I think that turntables are neat. They were once quite common on railroads, back when steam engines that needed to be turned to point the right direction were also common. Now, they are much more rare--rarer still to find one working.
As a work of engineering, they are quite interesting: on the central pivot they have a bridge which must easily support the weight of a locomotive but be able to turn smoothly in the pit.
This is a nifty style of turntable, either called an A-frame or a "gallows" turntable. A recently-constructed reproduction stands on the site of an 1867 turntable of the Sacramento Valley Railroad in downtown Folsom, California. In January, I visited the 5-inch scale, 15-inch gauge Redwood Valley Railway, in Tilden Park, Berkeley. They have a nice A-frame turntable, which exudes character with a mossy patina. It features an incomplete perimeter circle rail and pit wall--possible because the locomotive is balanced on the center while being spun. Also note the square "roundhouse". They actually use it, which is neat in-and-of-itself.
Simple, yet well-engineered, turntables are to me proof that not all railroad engineers just drive trains :-)