The County Hall is the centrepiece of the market square — a magnificent Grade I-listed building begun in 1678 and designed by Christopher Kempster, a mason who had worked under Christopher Wren on St Paul's. The arcaded ground floor was originally an open market hall, and the courtroom upstairs is now the museum's main gallery.
The collection runs from prehistoric finds along the upper Thames to Abingdon's MG car factory, which built sports cars in the town from 1929 until 1980. Climb to the rooftop viewing platform for the best view in town, looking across the rooftops to the Thames meadows and the spire of St Helen's. Entry is free.