Located in the hills east of Perth, Australia sits the historic Mundaring Weir Hotel surrounded by beautiful bush and close to Lake C. Y. O’Conner formed by the dam known as Mundaring Weir. The dam and reservoir form the boundary between the suburbs of Reservoir and Sawyers Valley. The dam impounds the Helena River. The lake created by the dam was known as the Helena River Reservoir, however it is now known as Lake C.Y. O’Connor.

A soldier, Ensign Robert Dale, became the first European to explore the region in 1829. European populations did not grow significantly until construction of the dam in the late 1890s. This involved the building of a railway line from Mundaring to the Mundaring Weir site. The Irish Australian engineer C. Y. O’Connor was involved the design of a scheme that transported water to the Eastern Goldfields of Coolgardie and Kalgoorlie in the eastern part of Western Australia.

The owner of the dam, the Water Corporation, refers to the weir as Mundaring Dam on its website, but no other authority, such as Geographic Names, or Geosciences Australia uses this term. The Mundaring Shire uses an image of the Mundaring Weir in its logo.

Work commenced to raise the dam in the late 1940s, which was completed in November 1951. In the early 1970s the downstream dam from the weir—the ‘Lower Helena Pumpback Dam‘ was constructed. It last overflowed into the Helena Valley in 1996.

Mundaring Weir Hotel, previously known as the Reservoir Hotel, then the Goldfields Weir Hotel has been in the area since 1898. It was a crucial location where O’Connor stayed regularly during the construction of the weir. After a period of decline it has regained popularity in recent years becoming a get-away for Perth residents, due to the current owner, Jens Jorgensen who bought it in 1984. It has been the location of annual concerts which included David Helfgott concerts during and after his recovered career as concert pianist.