Lake Merced is a natural lake near Fort Funston. It used to be San Francisco's main fresh water supply but is now the emergency reserve (somewhat worrying as a previous earthquake caused much of Lake Merced to drain into the Pacific).
The lake is also the site of the Terry/Broderick duel where in 1859 the Chief Justice of the California Supreme Court (Terry) killed a US Senator (Broderick) in an argument over slavery.
The loop around the lake is a flat five mile path, unfortunately marred by heavy traffic and constant gunfire from clay pigeon shooting and/or the SFPD firing range.
Rob and Rudy at Lake Merced.
Gill and Rudy next to a sculpture called "Penguin's Prayer". Given the latitude I expect the penguin is praying for the next ice age.
Hike starts at: 37.712302, -122.489232.