Mesa Francia was the company neighbourhood for French technicians and officials, and it still carries Santa Rosalia's most distinctive architectural mood. The streets above the centre have wooden houses, shaded porches, and old industrial buildings rather than the plaza-and-mission pattern common elsewhere in Baja.
It is not a polished heritage district. That is part of the appeal. Walk it together with Museo El Boleo and the church, and the town starts to read as a complete mining port rather than a random stop between Guerrero Negro and Mulege.