There is not one Boise office market anymore; there are two. The gleaming new towers with column-free floors and abundant glass are leasing briskly at premium rents. The dated mid-century buildings a few blocks away, with their low ceilings and inefficient layouts, are struggling to fill space at any price.

This bifurcation — a flight to quality, in the industry's parlance — has become the defining dynamic of downtown commercial real estate. Tenants competing to attract workers back to the office want the amenities and prestige that only the newest buildings offer, and they are willing to pay for them, leaving the older stock stranded.

The consequences ripple outward. Owners of obsolete buildings face a brutal choice between costly reinvention and slow decline, and lenders are growing wary of the older assets on their books. Some of these buildings will be converted to housing or torn down entirely; others will simply sit, a drag on the very districts they occupy.

For a city accustomed to nothing but upward momentum, the two-tier market is an early lesson in the harder economics that maturity brings. Not every building rises with the tide.