Participatory urban planning is central to sustainable city-making, yet the technically demanding nature of such interventions often limits meaningful involvement by diverse publics. We introduce a scalable digital participation platform that embeds sustainability projects within a navigable digital twin. Citizens experience a guided virtual walkthrough with audio narration employing the method of loci and spatial anchoring to support mnemonic encoding and recall. This immersive interface is augmented by two purpose-built LLM assistants: one delivers source-grounded factual clarifications, while the other facilitates reflective discussion. We evaluated this system in a randomized controlled online experiment (N = 195) against conventional industry practices (static visualizations and text-based consultations). Results show that spatially anchored immersive presentation significantly improved information recall, which substantially shifted participants' attention from individual inconveniences to collective, community-oriented sustainability benefits. Consequently, participants provided significantly more constructive, solution-focused feedback to the (simulated) municipality. These findings establish a practical tool for cities and policymakers to foster inclusive, democratic participation in sustainability transitions.
@article{arxiv.2604.16348,
title = {Beyond the Townhall: Spatial Anchoring and LLM Agents for Scalable Participatory Urban Planning},
author = {Carina I Hausladen and Javier Argota Sánchez-Vaquerizo and Michael Siebenmann and Arthur Capozzi and Sachit Mahajan and Dirk Helbing},
journal= {arXiv preprint arXiv:2604.16348},
year = {2026}
}