  It was recently understood that if the swampland conjectures are confronted
to experiment they naturally point to a solution of the cosmological hierarchy
problem in which the smallness of the dark energy is ascribed to an internal
(dark) dimension with characteristic length-scale in the micron range. It was
later inferred that the universal coupling of the Standard Model fields to the
massive spin-2 Kaluza-Klein (KK) excitations of the graviton in the dark
dimension leads to a dark matter candidate. Since the partial decay widths of
KK gravitons into the visible sector must be relatively small to accommodate
experiment, the model is particularly challenging to probe. We show that the
model can accommodate neutrino masses associated to right-handed neutrinos
propagating in the bulk of the dark dimension with an additional constraint
imposed by neutrino oscillation data. After that, we study the impact of the KK
tower in cosmology. We show that the modulation of redshifted 21-cm lines
driven by ${\rm KK} \to \gamma \gamma$ could be within the reach of next
generation experiments (e.g. SKA and FARSIDE). We also show that indirect dark
matter searches could uncover the ${\rm KK} \to \gamma \gamma$ signal. These
two observations combined have the potential for model identification. Finally,
we explore the global structure of the inflationary phase and demonstrate that
the model parameters required for a successful uniform inflation driven by a
5-dimensional cosmological constant (corresponding to a flat region of the
5-dimensional potential) are natural.
