Treestump

Went to Norfolk for the day, just to check everything was still OK. We went for a wander up the riverbank after lunch. This is about halfway to the bridge.
The black mill is an ex-windpump, which (Monty Python references aside) used to be used to drain the marshes pictured for cattle to graze - the land here is a couple of meters below sea level, and the river is directly behind me. The windpumps have been replaced by a network of fewer, more powerful electric pumps interconnected by a a wider system of drainage dykes - local parlance for a ditch.

Incidentally, are there any other incidences of the same word referring to both an object and its exact opposite? (A dyke also being a raised earth bank, of course...)