Poo

My running club organised a visit to Crossness Pumping Station (obviously) the original sewage pumping station serving the whole of south London. (A similar system was completed later for North London) The whole system was designed by Sir Joseph Bazalgette and opened in 1865. He designed a network of pipes which flowed from west to east and were finally pumped up from the  sewers into a massive reservoir (127million gallons) and then released into the River Thames as tide ebbed each day. Obviously this didn't do a lot for the Thames but it did eradicate Cholera in the city among other things.
The site is run and being restored by a trust after Thames water abandoned and wanted to demolish it. 
There are 4 massive steam beam engines, one, The Prince Consort has been restored to working order and steams on limited opening days each year, yesterday was one of those days
The main pic is part of Prince Consort, the beams are visible on the floor above along with the incredible ironwork and decoration in the building (extras).
Well worth a visit whether you are interested in sewage or not..