We explore how multistakeholder recommender systems (MRSs) can impact urban tourism promotion. Usually, two conflicting goals are of interest: (i) to cut down the number of visitors at popular sites and (ii) to satisfy individual tourist preferences, often biased towards popular sites. By leveraging users' limited knowledge of the sites catalogue, we model and simulate interactions between tourists and an MRS that jointly optimises user utility and promotes less popular sites. Experiments based on data logs collected in tourist cities reveal that an MRS can lift user utility and at the same time reduce the number of visitors at popular sites, manifesting the so-called positive-sum impact. However, a delicate balance is crucial; under- or over-promotion of unpopular sites in recommendation lists can be adverse to both destination and user utilities.