Seven by seven, and all of it under fog

FOG hides the whole map until you walk it. San Francisco is one of the few big cities where finishing the job is genuinely imaginable, if your legs hold out.

San Francisco on the FOG map, with the fog burned off along a walked route over Telegraph Hill and Nob Hill.

Forty nine square miles, most of them tilted

San Francisco is seven miles by seven, and that hard edge is why people try to complete it. Everything is inside the same small square. The catch is that the grid was drawn with no regard whatsoever for the hills, so the streets simply go straight over them. Filbert between Hyde and Leavenworth is a 31 percent grade. The Filbert Steps on the east face of Telegraph Hill are not a street at all, they are wooden stairs running up through gardens.

Nob Hill, Russian Hill, Potrero, Bernal Heights and Twin Peaks all charge admission in vertical metres. A ten kilometre walk here is worth fifteen anywhere flat, and your route planning quickly becomes a matter of which climbs you are willing to pay for.

Two grids and a diagonal

Market Street runs diagonally across the city, and the grids on either side of it were laid out separately, which is why the intersections south of Market never line up with the ones north of it. It makes the SoMa side of downtown feel subtly wrong until you notice why.

West of Twin Peaks the city becomes something else. The Sunset and the Richmond are forty or fifty blocks of flat, regular, near identical avenues running out to the ocean. They are the easiest walking in the city and by far the least eventful. Golden Gate Park sits between them, three miles long, with the Panhandle running east from it toward the Haight, and the Great Highway along the beach at the far end.

An afternoon along the waterfront and up

Start at the Ferry Building. Follow the Embarcadero north to Pier 39, turn inland into North Beach along Columbus, and take the Filbert Steps up to Coit Tower. Come down the far side into Chinatown on Grant, climb Nob Hill, then drop over Russian Hill to the crooked block of Lombard. About nine kilometres with two proper climbs, and it crosses six neighbourhoods that feel nothing alike. If you have more in you, keep going west on Union into Cow Hollow and finish at the Marina Green.

Getting to a real percentage

A meaningful percentage of San Francisco is achievable, which is rare for a major city. The whole thing is about 121 square kilometres, and a determined walker can make a visible dent in a season. The north east fills fastest because the blocks are short and the neighbourhoods are stacked on top of each other. Downtown, the Mission and the Castro go quickly too.

The grind is the avenues. To move the number seriously you eventually have to walk the Sunset, and that means dozens of blocks that all look the same, in the wind, often in actual fog. Two honest notes to finish. In the Financial District canyon around Montgomery and Sansome, the towers bounce the signal and your track can wander a street sideways. Walking the same block on a clearer day usually fixes it. And the summer fog here is not a metaphor. July in the Outer Sunset is properly cold, and the best walking weather of the year arrives in September and October.

Questions people actually ask

Start with a dark map.

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