Dunning's Spring Park in Decorah is definitely worth a visit because you can see a 200-foot waterfall and an ice cave. There's a large gravel parking lot just off Ice Cave Road (labeled River Trail Trail Head on
Google Maps). From there, it's a 5-minute walk (0.2 mile) to see the waterfall.
After seeing the waterfall, head east on Ice Cave Road (which is closed to vehicles) to see the cave or you can take Huldra's Trail, which is a trail along the Upper Iowa River. I recommend bringing flashlights for the cave. Also, be aware that it's very slippery.
