The recent spread of participatory solutions opened new possibilities in the field of cartography and the dissemination of geospatial data. At the same time, the fast diffusion of open-source solutions for sharing geospatial datasets on the web allowed sustainable, low-cost tools for specialists worldwide. In this scenario, the University of Florence is running the T-PLACE research project, promoting educational, documentation, and exploration activities in the territory. Based on the participatory approach that characterises the entire project, this paper presents the development of a WebGIS platform that exploits a geospatial dataset based on Open Street Map (OSM). The aim is to start a sustainable process for participatory mapping of cultural itineraries founded on open-source solutions. The adopted solution integrates several open-source modules (Leaflet, Pyosmium, Three.js) using programming languages (HTML, JavaScript, Python, CSS), allowing the web map navigation of the geospatial context, with the possibility to visualise and navigate inside 3D environments and to automatically update the geospatial data with the participatory contribution of OSM users. The adopted framework can be a reference structure for community-based initiatives, municipalities, and companies who want to employ a low-cost, participative and sustainable solution for sharing cartographic information online.