If X is a complex variety, we can form a moduli space M of local systems parameterizing representations of pi_1(X). One would like to do the same in arithmetic situations -- if X is a curve over a finite field, or the ring of integers of a number field. Here we can only construct a shadow of M, remembering some of its formal geometry. However, there are many indications that a more satisfactory theory should exist, and I will review three of them in my talk.