  The pulsar wind nebula (PWN) HESS~J1825-137, known to exhibit strong energy
dependent morphology, was discovered by HESS in 2005. Powered by the pulsar
PSR~B1823-13, the TeV gamma-ray emitting nebula is significantly offset from
the pulsar. The asymmetric shape and 21~kyr characteristic age of the pulsar
suggest that HESS~J1825-137 is in an evolved state, having possibly already
undergone reverse shock interactions from the progenitor supernova. Given its
large angular extent, despite its 4~kpc distance, it may have the largest
intrinsic size of any TeV PWN so far detected. A rich dataset is currently
available with H.E.S.S., including H.E.S.S. II data with a low energy
threshold, enabling detailed studies of the source properties and environment.
We present new views of the changing nature of the PWN with energy, including
maps of the region and spectral studies.
