Harry's chimney is neat. Smokestacks are a visual reminder of the industrial-steam age and yet there's so few available in O-gauge. From my earlier thread, Melgar recommended Altoona Model Works, where I ended up buying the 16" kits. Very nice and heavy models, superb brick detail, good instructions. Maybe he can make taller units, or you could put the 16" behind a building to elevate even higher. For example, this one is sitting level with my industrial buildings, but you could customize a lower portion ~ 12" and wider diameter and install the 16" version one on top (anchor or glue down), to give requisite 28" tall.