A BRAZILIAN DIPLOMAT in Lisbon first mentioned Tróia to my husband and me soon after our arrival in the late 1960s. His enthusiastic description of the place sent us there on the next springlike Sunday. My husband, Alf, had been assigned as head of the political section at the U.S. Embassy in the Portuguese capital, pleased for his family at the prospect of a tour in Europe. As chargé d’affaires, he had closed down the Embassy in Cambodia two years previously and had spent a year at Princeton’s Woodrow Wilson School. We looked forward to learning about a culture new to us.

Tróia lies on the Sado River estuary off the southwest coast of Portugal — a narrow thirteen-mile long sand spit curved like a finger pointing into the open Atlantic. In summer in those days, regular ferries ran between the fishing port of Setúbal, which lies directly across the estuary, to the Tróia peninsula. The trip took about half an hour, the ferry moving through water the color of the intense sapphire blue seen in the pictures of Earth taken from space. In late winter the austere beauty of the peninsula was reminiscent of the windswept dunes of the Outer Banks of North Carolina. The seascape was not as rugged, however; and to gaze out on a February afternoon from the deserted shell-strewn beach of Tróia over the placid ripples of the Atlantic, a few seagulls wheeling overhead in the pale but warm sunlight, was to feel utterly removed from the bustle of Lisbon, a scant fifty miles away.

Tróia is thought to have once been an island that became linked at some indeterminate time to the mainland. Artifacts show it to have been inhabited since prehistoric days. Phoenicians and others navigating along the Portuguese coast evidently used it as a trading post. In about the first century A.D., the Romans built the town of Tróia (the ancient Cetóbriga) on the peninsula. The town lived mainly from fishing and salting and drying the catch. A tidal wave completely destroyed the town in 412 A.D. Centuries later, in 1858, salting tubs used for the fishing catch were reported to stretch for four kilometers along the Sado. In 1910, the ruins of the town of Tróia were designated a national monument and subsequent excavations dug up Roman glass and pottery, now on exhibit in Lisbon’s Museu Etnográfico. Roman bricks which had formed the tubs’ walls could still be found, as well as the occasional tip-tilted tub lying empty on the sand.

In 1968, when development of the peninsula as a tourist resort began to be considered and hotels planned, the Portuguese government again moved to protect the ruins and decreed a boundary beyond which construction was prohibited. On our first visit to the ruins in the spring of that year, our hired boatman told my husband Alf and me that official excavations would begin in the summer. On a later visit we found an ancient guard with a flowing white Mark Twain-like mustache installed in a weathered hut on a sandy hillock overlooking the site. Though he greeted us with the innate courtesy often found among the Portuguese, he made it plain that once official digging started, casual visitors Iike ourselves would be turned away.

It was too early for the regular ferry service on that first February visit of ours, but within a quarter of an hour, we were able to hire a sturdy motorboat in Setúbal. The captain’s young son, Manuel, served as crew. As we moved slowly past another boat in the harbor, I felt a moment of regret not to have hired that one, the impressive “Queen of the Sado,” but our launch, the “Tubal,” was spotless and her paint looked fresher than the Queen’s.

We’d been underway about ten minutes, the sparkling surface of the water splintering the sunlight into a million glinting reflections, when a glistening black dolphin suddenly arched up out of the water before curving gracefully back in. Six or eight others followed, cavorting slightly to port of us as though to guide our way. Later, we saw them in that same area several times, often in greater numbers. Once they leapt up some ten or twelve feet away in almost continuous procession. Were they playing with us or did we disturb them? Where the Sado meets the Atlantic must make for a fertile feeding area. Perhaps a Loch Ness monster or other interesting specimen lurked there too.

Shouting through the engine’s roar, João, our boatman, asked if we wanted to stop first at the ruins before going over to the beaches. We nodded; he steered further to port and finally stopped the boat some twenty feet from shore, just west of a small inlet. There was no dock but Manuel ushered us into the small dinghy at the stern and rowed us to shore until the dinghy scraped bottom. The stony shore was extraordinarily thick with shells and looked utterly peaceful, undisturbed by time or cataclysm. Green algae on the stones at the water’s edge and further into deeper water marked the boundaries of the tides.

“The Roman ruins are up there — in back.” The boy pointed toward some rough bushes along the top of a sandbank which rose steeply eight or ten feet above us. Still barefoot after wading ashore, we climbed up the slope, sliding back an inch or two for every forward step. From the top we scrambled down into a sand-covered complex of walls of varying heights which separated level areas from dun-colored mounds. Altogether it extended some hundred and twenty feet in length. The sand burned my bare soles. I bent over to slip my sandals back on. A triangle of dull terracotta caught my eye. Brushing the sand off, I uncovered and picked up an amphora handle about four inches long, a thumb print clearly visible at one end.

Manuel smiled at my delight. “About five years ago,” he said in careful Portuguese, “my father picked up a coin from the shore here. Later, he showed it to a professor who hired our boat and the professor said it was a valuable antique Roman coin. He bought it from my father to put in a museum.

“A horse lives here, too,” he said. “He swims in the water.”

A humming sound distracted us from asking more about the horse. Loud buzzing came from the sandy mounds, which were perforated by numerous holes that bees might have made. Sand covered most of the ruins. Although they were on the inner side of the peninsula, sheltered from the Atlantic, nothing held back the shifting sands, blowing through the centuries. Probably only the local fishermen and the occasional goat, like the one or two grazing nearby, could have known the ruins were there.

It was hard to make out the plan of the town. Obviously, little recent digging had been carried out. Further inland, there was a patch of black and white mosaic bits of a Roman floor which had been cemented, perhaps to preserve it. Portugal is a storehouse of ancient treasures and of innumerable historical and artistic objects. But the time and the funds for their preservation always seem to be in short supply.

The scent of wild thyme hung in the hot, still air. It was getting too hot to poke about much longer. Bounded by sand on all sides, the site was low, airless, closed in. Retracing our steps, we were soon back in the boat, headed west. As we rounded the curve of land hiding the site, we saw several men stooped and bending along the quiet shore of the inlet that separated the ruins from the beach area. They were digging for clams, João said. He told us this area was very rich in shellfish.

A few minutes later, we drew up at a floating dock attached to shore by a narrow wooden boardwalk. Asking João to come back for us around four-thirty, we unloaded our picnic and set off for the beach. A few wooden row houses ran along a narrow road to the Ieft. After passing a small shuttered ticket house at the end of the boardwalk, we followed along the empty shore to the right.

It was good to get away from the capital. The period of Alf’s assignment to the American Embassy in Lisbon happened to coincide with the last years of the Salazar government and there was a general feeling that time was running out for the forty-year dictatorship. It must end soon, but since no one knew what might happen afterwards, a feeling of uncertainty underlay our outwardly placid lives in Lisbon.

Across the estuary, Setúbal in its hazy setting of bluish foothills and the rugged cliffs of the Arrábida range looked satisfyingly far off. But around the next curve we found five or si:x young men in swimming trunks listening to a guitar player as they sat in a circle on a sandy hillock overlooking the beach. No one else was enjoying the early bonus of a beautiful spring day and beyond them stretched miles of empty beach.

The water, although too cold for swimming, was clear, calm, and good to wade in. After lunch I fell asleep to the sound of lazy ripples lapping the shore. Afterwards, we walked to the tip of the peninsula. Here the water was agitated, and further out, conflicting currents broke into frothy wavelets. The shells were larger and birds walked on the sand inland from us; when we tried to approach them, they skittered away, keeping their distance, but not flying off.

Back to the dock. lf we missed our boat, we might be stranded. A happy thought — but Alf reminded me the next day was a work day. Besides, signs near the closed ticket booth clearly said ‘No Overnighting.’

As we approached the pier, we heard a furious quarrel. Moored lengthwise, one boat took up all the space; ours was moored behind it. Never mind, we said without effect, trying to soothe ruffled tempers all around as we scrambled over the first boat onto ours. Loud denunciations were still being shouted over the widening area of water between the two boats when I interrupted.

“What is that swimming over there?” João looked over toward the inlet. ’’No — further over,” I said. “Near the side of the ruins.”

“Oh, that’s only the horse,” he said. Manuel smiled and nodded at us.

“But what is he doing in the water? Where is he going?”

“He lives on this side,” João said. “But he likes to go over to eat on the side where the ruins are. So he spends every day there and swims back at night.” For years the animal had followed this routine, he told us. João remembered watching it swim across when he was younger. The horse belonged to a wealthy family that summered on the peninsula.

“Watch him get out of the water,” he said, slowing the boat to a stop. The sleek dark head that had been moving deliberately across the inlet about half a mile away, scarcely moving the surface of the water, suddenly rose higher as it neared the shore. A long neck followed, and then the full body reared abruptly out of the water, dripping Iike some apparition from the deep. Scrambling onto the rocky shore, he paused a moment on a level area, shook himself, and then trotted inland, finally disappearing behind some trees.

When we started up again in our boat, drawing towards Setúbal, no other living thing appeared from the ruins of Tróia though I watched carefully until the shoreline became indistinct.

On subsequent visits, we never again saw the horse. Since then, of course, a lot of water has flowed past Tróia and under Portuguese bridges, and like other vestiges of that time that have been swept away, the horse must be long gone.