  How to construct the $d+1$ dimensional geometry explicitly from the dual
CFT$_d$ is a widely concerned problem. Specifically, given entanglement
entropies of a CFT$_2$, which is purely expressed by two dimensional
parameters, can we build the dual three dimensional geometry unambiguously? To
do this, one must assume nothing is known about the three dimensional geometry
and starts with the most general setup. In this paper, by identifying the UV
and IR entanglement entropies of a perturbed CFT$_2$ with the geodesic lengths,
we show that, the dual geometry is uniquely determined to be asymptotic
AdS$_3$. The holographic dimension is generated by the energy cut-off of the
CFT$_2$, according to the holographic principle. The pure AdS$_3$ is obtained
by taking the massless limit. Our derivations apply to both static and
covariant scenarios. Moreover, what deserves special attention is that the
ratio of the numberical factors of the UV/IR entanglement entropies are crucial
to have a dual geometry. We are led to conjecture a necessary condition of
holographic CFT$_2$.
