Because a picture is often worth far more than a thousand words, and I rode my bike by the Xcel Energy equipment yard in Boulder, here are some pictures of a transformer like the one that should be in Topeka or coming soon. The transformer to the left is 750 kVA, 120/208V; in the back you can see the cooling fins that all of these larger transformers have.
My bicycle is in the first picture for scale; the outside diameter of those wheels is about 27 inches. The second picture shows how these transformers are typically labeled. This is the size typically used for an 8-stall Supercharger Site, 500 kVA: 277/480 Volts. Maybe this one will be on its way to the new Denver Supercharger Site soon...but I assume that Xcel has another equipment yard closer to the Denver Site.
Happy Transformer Hunting!!!