Real World Street is the Target

How would you approach a scenario where I have an app that people can move through the city and when targeting certain landmarks/ buildings they would trigger Unity events?

The Developer Portal shows how to scan smaller objects to work with Model Targets. Would the process be simillar for my buildings? Is that possible taking into account that I can only photograph the building from limited vantage points from the street? Or do you think some kind of Location tracker such as GPS would be the only way to achieve it?

Thx