  We resolve the domain-wall structure of the model antiferromagnet
$\text{Cr}_2\text{O}_3$ using nanoscale scanning diamond magnetometry and
second-harmonic-generation microscopy. We find that the 180$^\circ$ domain
walls are predominantly Bloch-like, and can co-exist with N\'eel walls in
crystals with significant in-plane anisotropy. In the latter case, N\'eel walls
that run perpendicular to a magnetic easy axis acquire a well-defined
chirality. We further report quantitative measurement of the domain-wall width
and surface magnetization. Our results provide fundamental input and an
experimental methodology for the understanding of domain walls in pure,
intrinsic antiferromagnets, which is relevant to achieve electrical control of
domain-wall motion in antiferromagnetic compounds.
