Begun as a dream more than a decade ago, the construction of the Rosslyn Metro station - like that of the rest of this region's first venture into rapid transit - will always be a wonder.

It cost $42 million and a man's life to build it. A 103-foot-long escalator carries passengers down to trains that take them 85 feet below the surface of the Potomac River, through tunnels that were blasted out of solid rock four feet at a time. Nearly 130 men worked 24 hours a day in three shifts to complete it.

Since the idea of a subway system first began to take shape in the area in the early 1960s, the Rosslyn station had been a part of the plan. "From the beginning," said a Metro spokesman, "Arlington county saw the advantages of the subway and pressed hard for a station in Rosslyn."

In many ways, it was an easy call. From the 19th century, Rosslyn had been a transportation way station.In the 1800s, it was the place where the C&O Canal connected the capital with the nation west of the Potomac. In the 1900s, it was the place where the city's trolley cars turned around.

And in the 1960s, Rosslyn redevelopment was geared around the coming of the subway station, from the way the traffic was supposed to circulate to the number of parking spaces the county permitted in the underground garages. The number of spaces needed, according to one planner, was deliberately underestimated in the hopes that visitors to Rosslyn would eventually come in subway cars instead of station wagons.

After working closely with Arlington county planners over the station's location and appearance, Metro officials gave the go-ahead to a San Francisco firm, Bechtel Associates, in 1969. Less than two years later, the blueprints were in hand.

In 1971 construction workers began excavation for the tunnels that would connect the Foggy Bottom station with the Rosslyn station. Each of the two tunnels is 6,247 feet long, a third of that distance underwater. Their construction was one of the most difficult and time-consuming aspects of the Rosslyn project.

The workmen tunneled nearly 100 feet below the water, using what Metro construction engineer G. Thomas Prince called the "drill and blast method." Workmen would drill four feet into the rock, fill the space with explosives, and then come in with heavy equipment to drag out the muck left after the explosion had reduced the rock to rubble. They averaged about 12 feet a day.

According to Prince, construction workers had little problem with river water leaking into the tunnel. "It would have been dangerous," Prince said, "if there had been large fractures in the rock through which the water could leak." But, he said, the only real problem with leakage occurred around the Foggy Bottom station, where the rock near Rock Creek was not as dense as it was under the river.

As the workmen tunneled under the Potomac, those assigned to the station's site on N. Moore Street carved a 52-feet high cavern out of the rock 105 feet below the surface. The station had to be deep in Rosslyn, Prince said. It had to be deep enough to get below the 40 feet of soil on top of the rock and deep enough to join the tunnels across the Potomac that could rise out of the river at only a 4 per cent grade - at the rate of four feet vertically for every 100 feet horizontally.

The station was built in rock, Prince explained, because it ultimately was less expensive than constructing it in the soil above. When building in soil, he said expensive liners must be used to support the earth while the work is going on. Rock, for the most part, supports itself.

There were delays and ad hoc changes in the design. Prince pulled out a small file box filled with records of 76 such changes that had occurred throughout the station's construction, changes that ranged in cost from hundreds to thousands of dollars.

The intersection of two arches in the station took away some of the station's structural support and a huge steel-reinforced concrete beam had to be installed. The rock was not as good quality as the contractor expected, and the excavation went slower, drilling and blasting two feet at a time. In addition, the weaker rock meant that enormous steel ribs had to be built into the station to give it extra support. This caused the station's most expensive change, 4 million.

There was tragedy as well. In 1973, Richard Dossert, a 34-year-old electrician, died deep in the Rosslyn station when he was run over by a concrete mixer truck that was backing into the tunnel. Married and the father of two children, Dossert had been on the job less than a week.

Like the tunnel underneath the Potomac, the Rosslyn station was also excavated by the blast and drill method, this time in two-foot increments. Huge buckets hauled the muck out of the station. The leftover rubble was recycled. The U.S. Park Service used it to shore up the banks of the Potomac.

There were other causes for concern besides rock quality and construction delays. The station, after all, was built in the middle of busy Rosslyn.

Senior project engineer Edward A. Lassen recalled the controversy that developed when he and his staff tried to decide on the location of the station's 50-foot by 10-foot vent shafts. "Nobody had anything against vent shafts," Lassen said, "as long as they weren't located on their property."

Eventually, Lassen said, the vent shafts ended up straddling streets and sidewalks on N. Lynn and N. 19th Streets. And then there were the occasional broken stained glass windows in a nearby restaurant, the Orleans House, that were blown out by the force of the blasting.

By July of 1975, the structural work on the two-tiered station was complete, with lighting and air conditioning units already embedded in the concrete. Next came the 103-foot escalator, the elevators for the handicapped, the communications system, graphics, signal devices and a dozen other details that would comprise the completed station. Over a dozen primary contractors, Prince said, worked on the station.

The rail on which the subway cars would run came in 40-foot lengths. They were then welded into quarter mile sections and snaked into the station on dollies and laid end to end to Foggy Bottom.

On Dec. 14, 1976, the first subway train ran its trial run to Rosslyn Station. Work on the station continued up to the last minute as fare boxes were given the finishing touches just a few days before the first commuter came on board on Friday.

The station, Lassen says, was one of the more difficult ones in the system to design and build. Most of the construction at the station was done through a large hole cut into the surface rather than through the "cut and cover" method which involves exposing much of the area of a station and then covering it up with wooden planks.

In a sense, the work continues. In August, construction will begin on a 21-story office building, two stories of which will top the Rosslyn Station with a pedestrian plaza of stores and restaurants. The builder, Stanley Zupnik, said that his firm spent almost five years studying the city of Toronto "to see what a subway does to a city."

In three years' time, the final touches will be added to the station with the completion of the building. There will be elevated pedestrian walkways connecting the station to the buildings around it, and a second level added to the elevator for the handicapped. The complex, Zupnik said, will be "the hub of Rosslyn."

But beneath it, Metro's monument will remain.