The old Russo-Balt factory area around Valmieras iela is one of Riga's more offbeat industrial-history walks. The company built cars and aircraft here in the late Russian Empire, and the surviving late-19th-century buildings still show old plaques, signs, brickwork, and traces of the district's factory past.
The buildings are mostly seen from the street rather than visited inside. Come for the atmosphere and details, especially if you are interested in industrial architecture beyond the polished Art Nouveau centre.