Twitter's last day in San Francisco

iStock; Rebecca Zisser/BI

The other day I took a late-afternoon walk around the building formerly known as the headquarters of the company formerly known as Twitter.

From the front door of X, which is closing up shop in San Francisco on Friday, Market Street runs straight through downtown to the bay. In 1905 the famed urban planner Daniel Burnham called this spot "the center of the city." He wanted to make it a concourse intersected by an array of grand boulevards, like the spokes of a wheel.