  In a joint experimental and theoretical effort, we report on the formation of
a macro-droplet state in an ultracold bosonic gas of erbium atoms with strong
dipolar interactions. By precise tuning of the s-wave scattering length below
the so-called dipolar length, we observe a smooth crossover of the ground state
from a dilute Bose-Einstein condensate (BEC) to a dense macro-droplet state of
more than $10^4$ atoms. Based on the study of collective excitations and loss
features, we quantitative prove that quantum fluctuations stabilize the
ultracold gas far beyond the instability threshold imposed by mean-field
interactions. Finally, we perform expansion measurements, showing the evolution
of the normal BEC towards a three-dimensional self-bound state and show that
the interplay between quantum stabilization and three-body losses gives rise to
a minimal expansion velocity at a finite scattering length.
