Canterbury is one of the most important places in Britain from a historical, religous, and archaeological point of view, and it makes a worthwhile daytrip from London or a convenient stopover on the way between London and Dover. Christ Church Cathedral, the seat of Canterbury's Archbishop and the centre of the Anglican Church, is just huge and can be seen from a great distance. It's interesting, but overall I felt that except for its sheer size, there's not that much to distinguish it from Britain's many other cathedrals, some of which I thought were better and even more interesting (Durham, for example). I enjoyed St.Martin's a lot more, Britain's oldest church, where you are likely to be the only visitor and can take a closer look at the building and the surrounding cemetery. St.Augustine's Abbey seemed to be not much more than a collection of ruins, but you can see much of it from the outside of the archaeological area. All in all, a great place for a visit.