  We present three 43 GHz images and a single 86 GHz image of Markarian 501
from VLBA observations in 2005. The 86 GHz image shows a partially resolved
core with a flux density of about 200 mJy and a size of about 300 Schwarzschild
radii, similar to recent results by Giroletti et al. Extreme limb-brightening
is found in the inner parsec of the jet in the 43 GHz images, providing strong
observational support for a `spine-layer' structure at this distance from the
core. The jet is well resolved transverse to its axis, allowing Gaussian model
components to be fit to each limb of the jet. The spine-layer brightness ratio
and relative sizes, the jet opening angle, and a tentative detection of
superluminal motion in the layer are all discussed.
