Restraining the Helena River, Mundaring Weir is a concrete dam built in 1903 to the designs of engineer CY O'Connor as part of a dazzlingly ambitious scheme to supply water to the Kalgoorlie goldfields 560km to the east (the longest freshwater pipeline in the world…and it worked!). The reservoir is a blissful spot, with walking trails, kangaroos and a well-positioned pub. The best dam view is from the lookout just off Mundaring Weir Rd near the dam's southern end.
The Bibbulmun Track goes over the top of the dam. You can also check out the old No 1 Pumping Station nearby, with its towering red-brick chimney (noon to 4pm weekends, adult/child $8/5).