  We report on the observations of the quasar NRAO 530 with the Event Horizon
Telescope (EHT) on 2017 April 5-7, when NRAO 530 was used as a calibrator for
the EHT observations of Sagittarius A*. At z=0.902 this is the most distant
object imaged by the EHT so far. We reconstruct the first images of the source
at 230 GHz, at an unprecedented angular resolution of $\sim$ 20 $\mu$as, both
in total intensity and in linear polarization. We do not detect source
variability, allowing us to represent the whole data set with static images.
The images reveal a bright feature located on the southern end of the jet,
which we associate with the core. The feature is linearly polarized, with a
fractional polarization of $\sim$5-8% and has a sub-structure consisting of two
components. Their observed brightness temperature suggests that the energy
density of the jet is dominated by the magnetic field. The jet extends over 60
$\mu$as along a position angle PA$\sim -$28$^\circ$. It includes two features
with orthogonal directions of polarization (electric vector position angle,
EVPA), parallel and perpendicular to the jet axis, consistent with a helical
structure of the magnetic field in the jet. The outermost feature has a
particularly high degree of linear polarization, suggestive of a nearly uniform
magnetic field. Future EHT observations will probe the variability of the jet
structure on ${\mu}$as scales, while simultaneous multi-wavelength monitoring
will provide insight into the high energy emission origin.
