The city keeps trying to board up the old Metro entrances, but people just come along and rip the boards down. Ever since the tunnels flooded years back after the subway was first built, sidewalks have rumbled like they would to a train, except it’s the sound of the underground canals rushing from the Valley through Laurel Canyon to the Fairfax Corridor, then branching east to Hollywood and Silverlake beyond that, or south to Baldwin Hills. There the tunnels fork again: one winds toward the ghost marina and the other picks up the L.A. River and continues on toward San Pedro and the harbor. Sailing down the southward canals from any of the makeshift docks that riddle the underground, you pass transients living in catacombs and old abandoned subway cars floating in the grottos. Siamese-twin lizards skitter across the tunnel ceiling, and the deep white bleached roots of the trees that line Crescent Heights and Sixth Street crack through the subway walls. If you take the boat all the way out to Santa Monica the subterranean river deposits you out into the steaming bay, where a cobalt sky explodes above you and the city looms up in back, wreathed by a mane of smoke.