Not only do you have the cathedral which marks Wells as a city in the first place and the home of the Bishop of Bath and Wells, it also very compact. it is easy to wander from the cathedral green, along the oldest residential street in the UK (Vicar's Close) with stunning medieval architecture, across to the grounds of the Bishop's Palace, or through the often bustling market place to sample the many independent shops along the High Street and beyond.
Lovely eateries (The Good Earth being our favourite), a good range of pubs and cafes, and now a small micro pub (Just Ales). Good for charity shops too!
We go there often - usually to coincide with the Saturday or Wednesday markets. And almost everyone who does go enjoys it. For a good article on what to see and do check out this web article on the London-based Weekendr website: "24 Hours In: Wells".