I thought my first port of call should be the Sioux Falls themselves. The city grew up around them and now they are protected by an extensive park system along the Sioux River. While settlement had grown up from the native American period and then the first settlers, the city dramatically expanded with the coming of the railroad, but using the water power from the cascades in the vicinity allowed industrial plants to grow up. I could see the Falls Park would have probably looked pretty derelict and run down about 30 years back when those industries started to fail, but some inner city regeneration and some good landscaping around the river has now turned this once more into the historical heart of the city.
The falls are a phenomena from the ice age, which deposited huge amounts of the lumpy lands I had driven through earlier, but here eroded the bedrock, a shockingly pink form of quartzite, over which the Sioux River now fell. The river was very slowly cutting back making a small gorge and a number of cascades, the water splitting in to several channels that dance over the rocks with varying force. I parked up and wandered around the various viewpoints, then clambered over some of the rocks, but it was a cold day and the light was fading, I gave up and headed back towards the hotel, stopping off at a couple of stores to pick up what I hoped were my supplies for the week, and then collapsing on my very comfy bed to hope that the jetlag was receding.