@ConwellWesleyL-9715 Welcome to Microsoft Q&A forum! Thanks for your interest in Azure Digital Twins.
There are multiple resources available to start with it for modeling a smart city in the Azure Digital Twins.
Please go through the below list of examples and let us know if you need further help.
Create smart places by using Azure Digital Twins
Connecting urban environments with IoT and Digital Twins
Smart Cities Ontology for Digital Twins
You can also watch this IoT Show episode to learn how we approached the DTDL-based Smart Cities ontology, how we mapped the ETSI NGSI-LD models to DTDL, extending the ontology based on Saref4City, while bringing it all together with an example use case brought to life with Azure Digital Twins Explorer.
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