Victoria's largest natural freshwater lake lies about 20 km south of Rainbow. Like Wyperfeld's lakes, Lake Hindmarsh is ephemeral — it fills during periods of high rainfall when the Wimmera River system overflows, then gradually evaporates back to a flat, cracked clay pan. In a good year it attracts enormous numbers of waterbirds, including pelicans, cormorants, ibis, and various species of duck and wader. In a dry year it is a wide white pan, surreal in its emptiness.
The lake is accessible from Jeparit, about 30 km south of Rainbow. There are basic facilities on the lakeshore and a small museum in Jeparit devoted to John Curtin, Australia's wartime prime minister, who grew up in the town. The lake is worth visiting regardless of water levels — the flatness of the landscape and the scale of the sky are impressive in their own right.