  The Swampland Distance Conjecture states that at infinite distance in the
scalar moduli space an infinite tower of particles become exponentially
massless. We study this issue in the context of 4d type IIA and type IIB
Calabi-Yau compactifications. We find that for large moduli not only towers of
particles but also domain walls and strings become tensionless. We study in
detail the case of type IIA and IIB ${\cal N}=1$ CY orientifolds and show how
for infinite K\"ahler and/or complex structure moduli towers of domain walls
and strings become tensionless, depending on the particular direction in moduli
space. For the type IIA case we construct the monodromy orbits of domain walls
in detail. We study the structure of mass scales in these limits and find that
these towers may occur at the same scale as the fundamental string scale or the
KK scale making sometimes difficult an effective field theory description. The
structure of IIA and IIB towers are consistent with mirror symmetry, as long as
towers of exotic domain walls associated to non-geometric fluxes also appear.
We briefly discuss the issue of emergence within this context and the possible
implications for 4d vacua.
