  Following the advent of electromagnetic metamaterials at the turn of the
century, researchers working in other areas of wave physics have translated
concepts of electromagnetic metamaterials to acoustics, elastodynamics, as well
as to heat, mass and light diffusion processes. In elastodynamics, seismic
metamaterials have emerged in the last decade for soft soils structured at the
meter scale, and have been tested thanks to full-scale experiments on holey
soils five years ago. Born in the soil, seismic metamaterials grow
simultaneously on the field of tuned-resonators buried in the soil, around
building's foundations or near the soil-structure's interface, and on the field
of above-surface resonators. In this perspective article, we quickly recall
some research advances made in all these types of seismic metamaterials and we
further dress an inventory of which material parameters can be achieved and
which cannot, notably from the effective medium theory perspective. We finally
envision perspectives on future developments of large scale auxetic
metamaterials for building's foundations, forests of trees for seismic
protection and metamaterial-like transformed urbanism at the city scale.
