  These lecture notes are based on a series of lectures given at the XIII
Modave summer school in mathematical physics. We review the construction due to
Hamilton, Kabat, Lifschytz and Lowe for reconstructing local bulk operators
from CFT operators in the context of AdS/CFT and show how to recover bulk
correlation functions from this definition. Building on the work of these
authors, it has been noted that the bulk displays quantum error correcting
properties. We will discuss tensor network toy models to exemplify these
remarkable features. We will discuss the role of gauge invariance and of
diffeomorphism symmetry in the reconstruction of bulk operators. Lastly, we
provide another method of bulk reconstruction specified to AdS$_3$/CFT$_2$ in
which bulk operators create cross-cap states in the CFT.
