At the end of last year it was located in a basement room at Rotherham Central Library and Arts Centre. "It's a coup for little old Rotherham," says one volunteer.
The visit was arranged by Art Gallery organiser Sandy Nuttall, who says this has been "the biggest crowd-puller".When children come, the voluntary staff - mostly students or retired teachers - introduce them to the fundamental principle of the centre, that visitors should touch - and wash - their hands afterwards. Then they are let loose.Wild excitement is followed by intense absorption.
The first activity is measuring, weighing, feeling. You can assess the length of a real snake skin by pacing along it.
You lift a reindeer's antler to your head and marvel at its weight; consider the characteristics of a loofah, pine cones, a turtle shell, a fossil; make comparisons, ask and answer questions.
In an area devoted to the human body children are weighing themselves, sticking their tongues out for a mirror - very popular - and attempting to curl their tongues, usually unsuccessfully. "We'd have run miles for this in school, when I was teaching," says a retired primary head.
"Of course, you do the body, you do all the ordinary things, but you don't think of doing things like this."
Elsewhere, children can launch sycamore wings cut from paper and guess which will succeed in growing into trees. Is it the largest seed wing or the one furthest away from the parent tree?
School parties enter free. The costis shared between the Natural History Museum, the host venue and the sponsors, currently Marks and Spencers. Sandy Nuttall says she "nagged and nagged" to bring the exhibit to Rotherham.
The Natural History Museum provides two co-ordinators to train local volunteers.
At the end of a lively Friday afternoon those helpers were still enthusiastic. "The children bring so much energy, enjoy it so much, you don't really get tired," said one, "I could do another school now if you brought one in. "
Some of the children left still wanting another go - at the popular Feely Boxes or the seashore guessing game.
Shameen, two weeks in the country and with not a word of English, was delighted to get all the fossils right on the Find the Fossil game.
Those who wanted more probably brought their parents back on Saturday.
"There are some faces we see twice a week," says Sandy Nuttall.The children of Broom Valley Junior School added their excited comments: "It's brill, because of the Feely Boxes." Or, "Oh no, I were scared of the Feely Boxes!".
They'd be back.