This paper describes a comparative case study that aims to uncover the quantifiable differences between non-interactive and interactive public displays in the urban
environment. The study involved a large temporary
interactive public display on a central city square showing a selection of custom-made content. We have evaluated the effect on passers-by and spectators in two conditions: 1) non-interactive (2102 passers-by, 228 viewers), by showing a content loop, and 2) interactive (1676 passers-by, 257 viewers), by adding physical pushbuttons for content selection and gaming. We discuss the influence of noninteractive and interactive public displays on: 1) attracting attention, 2) engaging people, 3) improving social dynamics within and among groups of viewers, and 4) catering for the suitable time of day. Based on our observations, we provide quantitative support for the hypothesis that interactive displays are more successful than non-interactive displays to engage viewers, and to make city centers more lively and attractive.