Please answer a question about the following article about Philadelphia:

Rowing has been popular in Philadelphia since the 18th century. Boathouse Row is a symbol of Philadelphia's rich rowing history, and each Big Five member has its own boathouse. Philadelphia hosts numerous local and collegiate rowing clubs and competitions, including the annual Dad Vail Regatta, the largest intercollegiate rowing event in the U.S, the Stotesbury Cup Regatta, and the Head of the Schuylkill Regatta, all of which are held on the Schuylkill River. The regattas are hosted and organized by the Schuylkill Navy, an association of area rowing clubs that has produced numerous Olympic rowers.

What is the symbol of rowing in the city?
Boathouse Row