Queen Mary’s Steps

Queen Mary’s Steps, in the grounds of the Ministry of Defence gardens, are remnants of the steps used by Queen Mary (William and Mary) to get from the royal apartments, in the original Whitehall Palace, to the state barge on the Thames. Back then, the Thames was much wider than it is today.
 
Since the steps no longer function as a way of getting from (a) to (b), I think they can be classed as a “Thomasson.”