At a mere seven miles from coast to coast, San Francisco invites even the occasional hiker to traverse its breadth in a few short hours. A couple of years back we proposed a rather placid northerly route; this year's southern crossing is decidedly more vigorous. Start at Ocean Beach down around Lawton and head east. After three dozen level blocks ascend Grand View Park and enjoy an amazing 360-degree panorama of ocean, bay, and distant skyscraper. Continue on Lawton as it becomes Warren Drive and make your way up Mount Sutro, pausing now and then to contemplate the gargantuan antenna nearby. Find Clarendon Avenue and follow it to Twin Peaks Boulevard for further mountain climbing, this bout rewarded with a dazzling view and perhaps a vendor-supplied hot dog. Tumble down Twin Peaks to 24th Street and continue east, pausing for a nosh at the Noe Valley Bakery. Cross Dolores and enter the Mission just in time for your next snack, a tamale at La Barrasa Market. Thoroughly fueled, continue your trek, pausing for a glimpse at the Balmy Alley murals, then head north on Harrison to Mariposa to circumvent Potrero Hill (why kill yourself at this point?). Cross 101 and 280 and before you know it you're at the shores of the bay, sucking down an Anchor Steam at the Ramp. God knows you deserve it.