A change-of-use permit filed July 30 would convert a two-story office at 681 Harrison Street into an aroma therapy spa — logged in the city's records under the blunter heading "massage parlor." It's a small, honest signal of what downtown office square footage becomes when the tenants don't come back.

The paperwork is more specific than the block. On July 30, someone filed a permit to gut a two-story office at 681 Harrison Street and turn it into a spa — an "existing office space to be converted into an aroma therapy spa," in the application's own words, with a modified front door for accessible entry, an accessible lift, a new floor plan of partition walls, and a new accessible toilet. The estimated cost is $80,000. The permit number is 202607305842, an over-the-counter alteration, and as of this week its status is simply filed.

What the applicant calls an aroma therapy spa, the city calls something plainer. In the Department of Building Inspection's records, the "proposed use" field for 681 Harrison reads massage parlor — the bureaucratic bucket the city drops any bodywork business into, whatever the signage out front eventually says. The existing use is office; the occupancy classification, B, doesn't change. On paper, one kind of small commercial tenant is being swapped for another inside the same wood-frame shell.

The address sits on the 600 block of Harrison, between Second and Third, a block or so off the Bay Bridge touchdown in the stretch DataSF files under Financial District/South Beach, Supervisor District 6, ZIP 94107. It is not a tower. It's a two-story building, block 3763, lot 095 — the kind of modest structure that once held a back-office tenant and is now worth $80,000 to reconfigure for something walk-in.

The block around it is doing the same quiet arithmetic. Two doors down the corridor, 489 Harrison drew an $85,000 alteration permit that was issued July 29, the day before this one was filed. At 2 Harrison, near the water, a $300,000 alteration has been sitting filed since July 17. Individually they're line items. Together they're the sound of a corner reshuffling its uses one over-the-counter permit at a time.

There's a larger backdrop here — downtown office vacancy still hovering near record highs, square footage that isn't filling back up with desks. An office becoming a spa is one small, legible answer to the question of what that space turns into instead. It is not a verdict on anyone. It's a filing.

For now, that's all it is. Walk past 681 Harrison tomorrow and there is no spa — just a permit in the record, a lift and a toilet and some partition walls still on the drawing, and an office waiting to be something you can book an hour in.