The new Mormon Temple on Logan Square may be the most radical work of architecture built in Philadelphia in a half-century. Clearly, that's not because the gleaming classical tabernacle offers a fresh, 21st-century take on architectural form-making, or because the designers inventively use new materials, or because they stretch the limits of technology. It's radical because it dares to be so out of step with today's design sensibilities and our bottom-line culture.

There have been, of course, plenty of classically inspired designs in Philadelphia in recent years, most of them insipid. With their factory-made facade panels, plasticky windows, and awkward proportions, they are unconvincing pretenders, cynically dressed up with historical accessories. The Mormon Temple is the real classical deal.

Perhaps befitting a building inspired by the architectural language of Imperial Rome, the temple also represents a bold incursion into the hierarchical fabric of Philadelphia. Located on the northeast corner of Logan Square, the Mormon Temple has planted its flag on the city's premier civic, cultural, and religious space.

Separated by the chasm of the Vine Street Expressway, the alabaster-white Mormon Temple, which will serve about 41,000 members in parts of Pennsylvania, New Jersey, Delaware and Maryland, stands virtually parallel to the chocolate-brown Cathedral Basilica of SS. Peter and Paul, which claims 1.4 million Catholic faithful in Philadelphia and the Pennsylvania suburbs. The temple is nearly equal in size to the cathedral, and its assertive architecture trumpets its ambition for all to see.

The double-spired temple was jointly designed by two firms that generally are in the habit of making modern buildings, Perkins & Will in Atlanta and FKKR Architects in Salt Lake City, but they have gone all-in to make the Mormon sacred center a credible classical building.

The entire structure - from the plinth that grounds it to the tip of the 197-foot spire supporting the gold-leafed Angel Moroni - is encased in four-inch-thick Maine granite, hand-cut by master stonemasons in Quebec. The massing is rigorously symmetrical and hierarchical, and employs a rich classical vocabulary that includes Corinthian columns, pilasters, and window pediments. The quality of the interior woodwork, which includes handrails that feel like velvet to the touch, is exceptional.

Though the temple has just four occupied floors, its roof tops out at a generous 80 feet, the height of the former Family Court building next door. The cadences of the temple's Vine Street columns and windows pick up the precise patterns of the old courthouse, which was completed in 1941 and can be considered the last truly satisfying neoclassical design in Philadelphia.

Church officials won't say how much this all cost, but based on comparable projects, it couldn't have been less than $100 million. That estimate doesn't include what the Church of Jesus Christ of Latter-day Saints spent on the redbrick meetinghouse across the street, at 17th Street and Vine.

That strange, one-story structure was designed by Robert A.M. Stern, and it is the antithesis of the temple. It looks like a squashed cupcake with a giant candle stuck on top. Most baffling is the presence of a drainage basin on Vine, which is supposed to become the main street of a trio of Mormon buildings. An apartment house is going up on the next block, and its residents will have to pass the unfortunate facade every time they have religious business.

The basin is not the only misstep. Despite the Mormons' commitment to creating high-quality traditional architecture, they have been much less adept at replicating traditional urbanism.

To be fair, it was no easy task to establish a walkable streetscape in this location. The three-building complex was built on a sprawling parking lot overlooking the great canyon of I-676. Merely repopulating that big void with buildings will go a long way to reconnecting this part of the Logan Square neighborhood with Center City.

The problems along Vine actually start with the temple. Mormon tradition calls for temples to face east, toward Jerusalem. It is not mandatory, but preferred, says Elder Larry Y. Wilson, who oversees the construction of the group's religious buildings. Placing the temple's front door on 17th, facing east, also allowed it to line up with the front door of the meetinghouse.

The downside is that the temple turns its back on Logan Square. It occupies this important civic space without being a real participant.

It does help that the rear facade is as attractive as the front. The architects have also made an effort to engage the square by putting a side entrance on Vine, leading to a small courtyard. Yet, because the temple is elevated from the sidewalk by several feet, it still feels like an exclusive compound. Compare its entrance with the cathedral's, which meets the street with a short set of stairs, drawing visitors directly into its magnificent sanctuary. By contrast, once inside the temple, you don't even know that you're in Philadelphia, because all the windows are frosted with stained glass.

The temple is reserved only for important sacramental uses. It does not function as a gathering place in the way that churches and synagogues do. The regular religious services will take place in the meetinghouse.

From 17th, the temple does make a fine backdrop for wedding photos and selfies. The strongly vertical building has the proportions and coloring of a New England Congregational church wrought on a massive scale. Lavishly fitted out with Federalist-style millwork and colonial-style furnishings, the interior has the feel of a high-end but unfashionable hotel. The first thing you see when you walk through the great bronze doors is a reception desk.

Some might wonder why the Mormons chose the early American architectural style. Many of their most beloved temples, like the one in Washington, are unrepentantly modern.

Church elders said their goal was emphasize this temple's connection to the city where America was founded and the Constitution written. Like the Mormon religion, which was established in this country in 1830, it sees its story as intertwined with the invention of America.