Ales Stenar is a rock formation (in the shape of a ship, roughly) that sits atop a ridge on the coast of southern Sweden. There have been many comparisons to Stonehenge but there are no other connections other than they both have standing stones in a circle/oval. They've posted a few theories about why they exist which are worth a read. The short hike to the top of the ridge is easy enough and the views from the top provide sweeping views of the coast.
Ales Stenar (Ale's Stones) is a fascinating place to stop if you're driving in the vicinity; I wouldn't make that the only stop on your day trip. There's not really much to see around it and the little adjacent village doesn't have much to offer in the way of amenities but it is picturesque. Just keep your kids off the ancient stones!