  We study four-dimensional heterotic flux vacua with N=2 spacetime
supersymmetry. A worldsheet perspective is used to clarify quantization
conditions associated to the fluxes and the constraints these place on the
moduli spaces of resulting compactifications. We propose that these vacua fit
naturally in the context of heterotic/IIA duality as heterotic duals to
compactifications on K3-fibered but not elliptically fibered Calabi-Yau
three-folds. We present some examples of such potential dual pairs.
