  Detectors in particle physics, particularly when including cryogenic
components, are often enclosed in vessels that do not provide any physical or
visual access to the detectors themselves after installation. However, it can
be desirable for experiments to visually investigate the inside of the vessel.
The MicroBooNE cryostat hosts a TPC with sense-wire planes, which had to be
inspected for damage such as breakage or sagging. This paper describes an
approach to view the inside of the MicroBooNE cryostat with a setup of a camera
and a mirror through one of its cryogenic service nozzles. The paper describes
the camera and mirror chosen for the operation, the illumination, and the
mechanical structure of the setup. It explains how the system was operated and
demonstrates its performance.
