Moonlight tower

A moonlight tower or moontower is a lighting structure designed to illuminate areas of a town or city at night. The towers were popular in the late 19th century in cities across the United States and Europe; they were most common in the 1880s and 1890s. In some places they were used when standard street-lighting, using smaller, shorter, and more numerous lamps, was impractically expensive. In other places they were used in addition to gas street lighting. The towers were designed to illuminate areas often of several blocks at once, on the "high light" principle. Arc lamps, known for their exceptionally bright and harsh light, were the most common method of illumination. As incandescent electric street lighting became common, the prevalence of towers began to wane.

Photo of Los Angeles in 1882, via TheWayWeWere subreddit.