Where are the fuel tanks located in an Antonov An-225?
The 225 is derived from the An-124, which has 10 integral fuel tanks in the wings. Comparing the specs, it looks like fuel capacity is the same as the An-124, so the center section of the wing (the only new part of the wing) doesn't contain fuel.
Based on that, I think the tanks are in sections 2-6 and 13-17. I'm assuming the outer wing sections 1 and 18 are not used as tanks. If those were used as tanks you'd have higher loads on the wing during roll maneuvers.