  We demonstrate possibilities of a large scale multi-post re-entrant cavity
with two case studies implemented with the same physical structure. The first
demonstration implements two discrete Fabry-P{\'e}rot cavities crossing at the
centre. The configuration allows the control not only of the resonance
frequencies, but also a whole band gap and transmission band of frequencies
between the directly excited diagonal and a higher frequency band. The second
experiment demonstrates appearance of discrete Whispering Gallery Modes on a
circle of re-entrant post. With the introduction of an artificial "scatterer",
we demonstrate control over the doublet mode splitting.
