Originally published in Tube Times, San Francisco Bicycle Coalition newsletter 2003 (posted 2003)

On your way west from downtown, while rounding the turbulent corner from Duboce Avenue onto Steiner, you are probably thinking more about the blasting wind than about water, but it is water that has determined where you will ride.

As you continue toward the panhandle bike path, you don't need the guidance of the official "Bike Route 30" signs to turn from Pierce Street onto Haight and then Scott. In fact, you didn't need them the first time you rode this route. Why is that?

"The Wiggle" is the name bicyclists use for the zig-zag that you can easily follow, without guidance from signs, because it is the flattest route from Market Street to the Park.

Before humans used drills, picks and explosives against San Francisco's bedrock, it was gradually shaped by scouring rainwater. Water goes down the flattest route most easily; bicycles go up. This is what bonds the cyclist to the original topography of the land. Just as water knows without schooling how to handle high ground, so too does the bicyclist. We simply turn left or right, whichever is less steep, until we reach our lofty destination.

The greenish serpentine bedrock that lies diagonally under the area is more easily eroded than the flint-like chert. Long ago, before this valley went by the name Sans Souci, winter runoff carved the serpentine flat between two sets of hills. Buena Vista Park and Carona Heights are chert. The truncated hillside of the U.S. Mint provides clearly visible serpentine, across from the Duboce Bikeway Mural at Church Street.

If you look closely at the mural, you'll see in Sans Souci Creek the names of the streets you are following, cavorting on the flowing surface. The two types of rock are shown on opposite sides of the stream, as in the real world of the Wiggle. To this day, the creek flows in (and in the mural, into) the sewer.

If your ride brings you across the undulating surface of another landscape in a different part of town, you are probably following another water-carved wiggle—at least when headed uphill. Perhaps a stretch of street along your wiggle, too, can be reclaimed from car uses, as was Duboce in 1998, easing your flow, like the water that shaped this land we live upon.

A city is more than a city. Underneath it all, a city is still the place that it was before the first building was built, before the first path was trod. The topography of a land determines the city it can become.

Often someone who hasn't biked or walked the web of San Francisco streets responds to the mention of bicycling with, "You must be really strong!" I say accept the compliment and then assure them that the key to the hills is knowing how to go around them.