Chinese Temple
Built in 1863, this temple served the needs of all the Chinese north of Sacramento. Now it is a museum open to the public showing the history of the Chinese in the area as well as artifacts from the days when the temple was in full service.
Lake Oroville Visitor Center
While not actually in the town, this state-run visitor center offers a splendid observation of the town as well as the history of the construction of the lake and the Indian tribes that were in the area.
Oroville Dam
Billed as the largest earth-filled dam in the world, it is the tallest dam in the United States at 230m/770ft, and the top of the dam spans 2,110m/6,920ft. The view over the Sacramento Valley is stunning, especially after a good rainstorm. Just be advised that due to some reason given in the name of possible terrorism, you can't park directly on the top of the dam. There are also quite impressive tours under the dam showing the massive hydroelectric turbines, although the hours and offer of these tours are unpredictable.
Cherokee Ghost Town
What was once a boom town during the mining days, this is a small ghost town with several structures you can walk through from the road including what was the Wells Fargo Bank. There is also a small museum that has varying opening hours. There are a few scattered places where people still live, so tread carefully.