  In high magnetic fields ($B$), two dimensional electron systems (2DESs) can
form a number of phases in which interelectron repulsion plays the central
role, since the kinetic energy is frozen out by Landau quantization. These
phases include the well-known liquids of the fractional quantum Hall effect
(FQHE), as well as solid phases with broken spatial symmetry and crystalline
order. Solids can occur at the low Landau filling ($\nu$) termination of the
FQHE series, but also within integer quantum Hall effects (IQHEs). Here, we
present microwave spectroscopy studies of wide quantum wells (WQWs). The
spectra clearly reveal two distinct solid phases, hidden within what in dc
transport would be the zero diagonal conductivity of an integer quantum Hall
effect state. Explanation of these solids is not possible with the simple
picture of a Wigner solid (WS) of ordinary (quasi) electrons or holes.
