Downtown Santiago can be a bit of a slog when it comes to finding good running streets, but the high-end Vitacura neighborhood, in the northwest part of the city, is an exception to the rule. The Chile Road Runners, a team of the city’s foremost runners and triathletes, favor a 7K circuit starting at Parque Avenida Americo Vespucio. This long corridor park has a nice multi-use path running its length that you can follow from north to south before turning left onto Avenida Presidente Kennedy. At the futbol (soccer) pitch, head north on Avenida Manquehue Norte. This will take you through the center of Vitacura before meeting up with the path along Rio Mapoche, which will carry you back to the start.
If you prefer a 10K with minimal navigation required, you can stay on Vespucio for the length of the park (until reaching Avenida Francisco Bilbao) and double back.