The paper develops a concept for a digital tourism service intended to support independent exploration of cultural heritage in a historic city and provide access to guided excursions when needed. The study considers mobile cultural-tourism services and focuses on the functions through which a visitor can plan a route and receive historical information directly at the site. The purpose is to substantiate the project model of the Nizhny AR service for Nizhny Novgorod. The study combines a review of Russian and international publications on tourism digitalization and augmented reality with a comparison of the functions publicly available in existing tourism platforms. The sample includes izi.TRAVEL, VoiceMap, SmartGuide, Google Arts & Culture, RUSSPASS, RUSSPASS.Travel, Artefact, and Discover Moscow. The comparison indicates that the services usually concentrate on particular tasks: navigation, audio guides, cultural content, or AR. Their combination within one regional product remains uncommon. The proposed Nizhny AR concept brings together thematic routes, digital profiles of heritage sites, AR scenes, recommendations, and information on local tourism infrastructure. The proposed model can be used as a basis for an MVP and adapted for similar digital tourism projects in other historic cities of Russia.