A keyhole-shaped passage connecting two “lobes” of a former quarry passes beneath West Avenue in Elmhurst.
A keyhole-shaped passageway below a busy street connects two lobes of a 200-foot deep former limestone quarry in Elmhurst.
Though an observation deck overlooking the east lobe has been in place for a few years, this image from a drone provides an up-close view of the opposite side, where the keyhole passes beneath West Avenue.
On bright, sunny days, the keyhole’s interior is quite dark and difficult to see through. But in this view, taken on a hazy day, daylight is visible on the other side.
With the exception of the view available from the observation deck, the keyhole is difficult to see from the ground, due to tree growth and security fencing, and a casual observer might not even be aware of its existence.
Elmhurst-Chicago Stone began operations in the location in 1883, and the quarry was sold to DuPage County in 1992, according to the company’s website, ecstone.com.
It has been used for stormwater management since 1996.
According to DuPage County’s website dupageco.org, floodwater is diverted east from nearby Salt Creek, through a drop shaft, into 400-foot tunnel passing beneath Route 83.
It then passes through an open channel in the west lobe, through the keyhole, and into the east lobe where it remains until it can be pumped back into Salt Creek at safe flow rates.
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