Two radically different forms of electrical activity can be observed in the rat hippocampus: spikes and local field potentials (LFPs). Hippocampal pyramidal neurons are mostly silent, yet spike vigorously as the subject encounters particular locations in its environment. In contrast, LFPs appear to lack place-selectivity, persisting regardless of the rat’s location. Recently, we found that in fact one can recover from LFPs the spatial information present in the underlying neuronal population, showing how these two signals are two sides of the same coin. Nonetheless, there are many aspects of the LFP that remain mysterious. I will review several observations and explanatory gaps which await further study. These include: the relationship of LFP patterns to anatomy; the elusive structure of gamma waves; complex forms of cross-frequency coupling; variations in LFP patterns seen when the rat explores its world more freely; reconciling the memory and navigation roles of the hippocampus.