The metro in Mexico City uses beautiful icons for each of its 195 stations. I can confirm from my own experience using the metro during visits over the years that it works really well as a system for wayfinding. From the Guardian:
When work began in 1967, Mexico City’s metro system signified a dramatic modernisation of the cityscape. Making room for the metro meant clearing away some familiar aspects of the urban landscape, as well as introducing residents to the strange new spaces of the network’s underground tunnels and stations.
To integrate this new layer of urban infrastructure with the existing city’s pre-Columbian, colonial, and contemporary layers, the authors of the subway relied on a pictographic system. Lance Wyman, a New York-based graphic designer, designed icons to identify each metro station.
Instead of a name, this new geographic entity was visually connected to an existing historical or geographical feature. Thus the sign for Balderas station, where Line 1 met Line 3 in the historic centre, referenced a cannon on display in a library above-ground, while nearby Pino Suarez station was identified by the Aztec ruin that was uncovered (and destroyed) during excavations for the station.
Wyman’s pictorial system connected the surface to the subterranean. He created a visible match between the familiar spaces of the city, which were now connected to the new stations via street signs, and the far more abstract underground space of the metro system.