This lady is all the way from New Zealand and whilst on a round the world trip takes in canal boating.
She's half way to Chester from Middlewich.
That round brick building would have been a toll booth in it's day during the 1700 & 1800's, and would be a refuge for the lock keeper during the day. This would have been a very busy working canal, as it terminates at one end at Ellesmere Port on the River Mersey which is open to the sea.
There are 3 such round buildings on this stretch of the canal, each by a lock, the domed roof is made of carefully laid bricks and then covered in tar. A pot bellied cast iron stove with chimney out thro the roof would have been in the centre of the floor, with wooden (probably ash) seating around the wall.