Uncertain implies there’s at least a guess. What is it?
Wiki sez:
Its age is unknown, as several theories claim that Tarr Steps dates from the Bronze Age but others date them from around 1400 AD.
It must be maintained, right? I can’t imagine those flat stones all holding on through every flood for 600 years.
It has been restored several times in recent years, following flood damage. Over the years the damage provides a good indicator of the strength of each flood. Some of the top slabs have been washed away in extreme flood conditions and they have now all been numbered to facilitate replacement. The Exmoor National Park web site says
The stones forming the spans weigh between one and two tons each and have on occasions been washed up to 50 yards (46 m) downstream.
