This is DC Water’s Main Pumping Station, built in the Beaux Arts style in 1905 and renovated in 2005. It handles up to 400 million gallons of wastewater a day and is one of nine such station throughout DC. There were many signs for historic buildings in the waterfront area, such as a foundry and ammunition plant, but none save this one seems to have survived, although the Washington Navy Yard is still standing and in use, several blocks away.

Gone fishing, posted earlier.