So don't be surprised if you have trouble finding the front door when you arrive at the Postal Service's new Philadelphia flagship at 30th and Chestnut Streets. Both public entrances are recessed into the facade to the point of invisibility, and one even lacks an overhead sign. Could it be the agency's way of sending us a message, like "Stop with all those cards and letters"?

The Chestnut Street facility was built to replace the grand Depression-era fortress on the Schuylkill, which is being converted to offices for the Internal Revenue Service. But it's hard to believe the new $18 million building is meant to serve as the city's main post office.

This bean counter's dream has been shoehorned into the ground floor of a parking garage, which was dressed up for the occasion in a coat of perforated metal by the architects at KlingStubbins. There are big-box stores that convey a greater sense of civic majesty.

We can accept that America's post offices - even one anointed as the city's main location - need less space than they did when the monumental, limestone-clad 30th Street facility opened in 1936. It's no longer necessary to house the region's entire mail-sorting operation in the central branch. That's why Philadelphia's automated processing lines were moved to a new building near the airport and I-95 in 2006.

And now that we can e-mail a note around the globe in seconds and print stamps from our home computers, the main post office obviously plays a different role in our civic life. It's more of a retail experience. We're more likely to arrive lugging packages instead of letters.

Yet we still come to perform important civic duties, such as mailing our tax forms and applying for passports. Given that providing reliable mail service remains one of a government's most fundamental tasks, it's not unreasonable for citizens to expect to conduct their business in a space more dignified than a check-cashing outlet.

The old 30th Street post office, designed by Rankin & Kellogg, was by no means flawless, despite its size and prominence. Its entrances are also too small for its gargantuan scale and, bizarrely, none face Center City. Yet its public postal lobby is a magnificent art deco affair decorated in travertine and walnut. The elaborate detailing, which includes stylized, pre-Columbian-influenced reliefs, made waiting in line a pleasure.

Sadly, the federal government demanded that the lobby be taken out of service as a condition of the IRS lease. Why Washington thinks the space poses more of a security risk with the IRS as the main tenant than it did when all the city's mail passed through the building is a mystery.

The new central post office is a brighter, better-lit space, with natural light cascading in from a row of windows. But with a view of a Drexel University parking lot, it offers little in the way of architectural uplift. The designers at KlingStubbins say they were obliged to outfit the interior according to the post office's standards, which mandate the same blue laminate and cinderblock treatment regardless of whether the location is in a major downtown or astride a highway.

On the exterior, you can see that the architects worked hard to give the low-budget facade a bit of flash, and there are some deft details, including asymmetrical red and blue stripes and a screen edge that flies off the building. Yet those are design moves that look best glimpsed out of the corner of your eye as you drive by at night. On the ground, the effect is utterly soul-sapping.

Walking west from Center City, you're confronted with a long series of opaque, papered-over windows and a daunting, 320-foot-long facade. Because the post office is located in an old garage, the corners were occupied by stairs, normally a logical place for an entrance. But couldn't the architects have found something more zippy and graphic than gray paper to hide them? The decision to deeply recess the entrance doors was also a big mistake. They're invisible until you're in front of them.

As a result, it's not immediately clear how to get inside, especially if you happen to be in a wheelchair. There's an accessible entrance at the west end, but nothing clues you in to that fact.

If you look up, you'll eventually notice some metal grates protruding limply from the facade to mark the doors. These vestigial canopies were apparently inspired by the bronze versions over the loading docks at the old post office, but they dissolve into the silver-colored exterior. One also wonders about using all that metal when another garage with a perforated metal screen is being built next door, by Pelli Clarke Pelli. Such tricks rarely work the second time.

Ironically, the new post office has been touted as the missing link that will finally knit together Center City and the university area of West Philadelphia. Because of its function, the destination probably will bring people to the no-man's land. And the Postal Service deserves credit for creating on-street parking next to the building.

But neither the convenient parking nor the ground-floor windows can make the new main post office a great civic space worthy of a big city. The sad part is, we once had a glorious main post office. But we allowed it to be sacrificed to our fear of crowds.