The little church steeple, made of wood 205 years ago and looking sharp with its fresh white paint and new metal roof, is lighted up at night now so that passersby can once again appreciate its simple beauty and its call, as the Jesuits say, to the greater glory of God.

Inside, the sanctuary has regained something of the crisp cubic clarity it had in 1794, when it was consecrated as Holy Trinity Catholic Church--then sitting all alone on a Georgetown hill. (On today's maps, the site can be pinpointed at 3513 N St. NW.)

It is safe to say the little church has not looked this good since 1850, when Holy Trinity abandoned the building as a worship space for a grand Greco-Roman edifice around the corner on 36th Street. After that, the smaller building was pressed into service as a school, a convent and parish offices--even its tower had been partitioned into tiny rooms.

Today, however, the building with its truncated steeple and no-nonsense facade is the most visible part of an $8 million architectural gift Holy Trinity parishioners provided their church in time for Christmas this year.

Well, almost in time. The sanctuary is pretty much done, but it will be a couple of months before it can be used for services, as contractors finish up the rest of a big job--offices, meeting rooms, workshops, storage hideaways, rehearsal halls and gardens that the church has been planning for more than a decade.

The architecture, by Kerns Group Architects of Arlington, is exemplary. Renovating and adding to a historic structure is a complicated, delicate business, particularly when every move is carefully watched (and second-guessed) by neighbors and official review boards. But the process worked well here. In some ways, the new architecture and the renovation are separate stories but both, fortunately, have happy endings.

In 1787, when the property was sold to John Carroll, who later would become the first American Catholic bishop, the deed stipulated the land be used "for the purpose of erecting a Chapple [sic] or house of worship." The use of the words "chapel" and "house"--and not church--was important.

Georgetown was then still a part of Maryland, where Catholics had not been permitted to practice their religion openly since the passage in 1704 of the former colony's "Act to Prevent the Growth of Popery." In response, Catholics had practiced "house masses" at "manor chapels," largely in southern Maryland. The wording of the deed of sale reflected a century's worth of caution.

This was a sad, ironic chapter in Maryland's history--the state had been founded, of course, as a colony to which English Catholics could escape from such prejudice. John Carroll's intention, in founding Holy Trinity--and also Georgetown University at about the same time--was to bring this chapter to a close.

Like many of Maryland's leading Catholics, Carroll had been nurtured on the ideals of the American Revolution. "Carroll bought into the whole American dream," says current Jesuit pastor Lawrence J. Madden--and, as we can see again today in the renovated space, the architecture of the original Holy Trinity building reflects this.

Though nowhere near as elaborate as the main rooms of the big Protestant churches of the day--the somewhat earlier Christ Church in Alexandria, for instance--the sanctuary is, likewise, an Enlightenment room. If anything, its simplicity adds to the effect.

Natural light from generously proportioned, transparent windows washes upon the thick white walls. The straightforward geometry, comprehensible at a glance, suggests that reason is welcome here. The proportions are not dwarfing. It is an atmosphere in which certain rights--such as religious freedom--might indeed be thought of as inalienable.

The renovated sanctuary, however, is by no means a replica of the room as it was in Carroll's day. The heavy wooden roof trusses have been exposed, giving a slightly more dynamic character to the space. And the artwork is contemporary.

Particularly notable among the commissioned works are the bronze candleholders by Washington sculptor John Dreyfuss, at once elegant and weighty. Two wonderful polychrome sculptures by Belgian artist Pazzy De Peuter give the room a psychic crackle--a Christ figure floating on the white north wall and a standing figure of Saint Ignatius of Loyola, founder of the Jesuit order, in a high niche in the tower. The saint looks down at departing worshipers with big, reprimanding eyes, and reminds them of their duties in the world out there with a gentle gesture of his right hand.

Nor are liturgical arrangements what they would have been in Carroll's time. In keeping with recommendations of the Second Vatican Council three decades ago, chairs are arranged in a U-configuration around the altar table. One of the reasons, Madden points out, is to focus on the community of worshipers rather than symbols of authority. It suggests, he says, a communion of the human worshipers "with the communion of saints."

A similar emphasis is evident in the new architecture. For Thomas Kerns and his associates (Sean Reilly, Brian Donnelly and Jonathan Glick, with Michael Vergason as the independent landscape architect) have succeeded in creating a community of buildings and spaces. This was by no means a foreordained result.

Even before the new construction, much of the site was occupied--there was the main church, two separate wings of Holy Trinity School, a free-standing rectory, a power plant, the old chapel and a parking lot that snaked between the buildings. To this mix the parish was proposing to add about 30,000 square feet of offices, meeting rooms and so on--the maximum density allowed by law.

"No, no, no," said the neighbors and the members of the Old Georgetown Review Board--repeatedly. Eventually, this opposition forced the parish to make a costly but efficacious decision to push much of the new space underground. In addition to adding more than $1 million to the project's price tag, this had the downside of placing some of the offices below ground--not a desirable working environment.

Yet the architectural upside was significant. The decision meant that the entire eastern wall of the old chapel would remain exposed--that the chapel, in effect, would continue to rule its part of the hill. It also enabled Kerns and colleagues to organize the exterior spaces more effectively--and to spread their architectural wings a bit, normally hard to do in such highly regulated historic districts.

The old chapel faces south, from the top of a steep embankment. Along its eastern side now is a welcoming outdoor terrace, framed by a wooden trellis (which nicely shields skylights for those below-grade offices) and two diminutive buildings, each distinctive in its way.

One is a foursquare red-brick storage shed that looks as if it could have been there for ages--unless you look quite closely. The other is an octagonal building made of limestone-like cast concrete--rather striking and stern. Although it appears to be a late-20th-century version of a tiny Renaissance chapel, it is simply an entryway for the multipurpose building behind, pumped up to play a major role in shaping a delightful outdoor place for weddings, funerals or solitary contemplation.

This same unusual, appealing mixture of formality and informality, of rigor and relaxation, characterizes even the less publicly visible parts of the large project. It may be that the best of the new architecture faces a little parking lot in the back, where the architects obviously felt freer. Yet though most of these rear elevations are modern in style, they are neatly tied into a varied architectural context. All views are taken advantage of--such as an opening to Georgetown University's Healy Hall tower--and small details paid attention to--a bay window placed on center axis with a public alley.

Such a blend of architectural and place-making skills is a pleasure to mind and eye. So, too, is that little Enlightenment chapel on the hill, lighted up at night.