Six blocks north of the Plaza de Armas, the Museo de La Ligua (Pedro Polanco 698, tel. 033/712143, museodelaligua [at] tie [dot] cl) is open 10 a.m.–1 p.m. and 3:30–6:30 p.m. weekdays, 10 a.m.–2 p.m. Saturday; admission costs US$1.
Occupying the erstwhile abattoir, La Ligua [1]’s municipal museum might not justify a trip in its own right, but its exhibits on the early Molle and Ánimas cultures, through the Aymara, Mapuche, and Diaguita/Inka who successively dominated the area, merit at least a brief stopover.
It also deals with issues of cultural change during colonial times through institutions such as the encomienda, the 19th-century mining industry, and 20th-century urban development.
Links:
[1] http://www.moon.com/destinations/chile/chilean-heartland/vicinity-vina-del-mar/la-ligua