They are like the brooding remains of some ancient lost city.
Block after block of five-story sandstone structures, their arched porticoes opening onto rows of one-room shops, appear to be pocked and worn by centuries of wind and rain. Aside from an occasional stray cat, little disturbs the wasteland.
This used to be the heart of the city of Beirut. But from the start of Lebanon's civil war in 1975 until two months ago the capital's main commercial district became a free-fire zone between east and west Beirut. Shops were abandoned and looted, the buildings blasted by bullets and rockets.
Beirut's shattered center is a symbol of this country's broader devastation - the result both of civil war and of Israeli invasion against Palestinian resistance.
But today, with Beirut reunited, there is a new chance to rebuild the capital as well as the countryside. It will take more than bricks and mortar and optimism. It will take a genuine healing of the internal and external conditions that turned this country upside down. For this, there is still a long way to go.
A start, however, is already under way. Throughout most of Beirut, rubble is being cleared from streets, apartments are being mended, and structures damaged beyond use are being pulled down. Concrete and glass prices have increased sharply. Employment is being given a boost.
To rebuild after an earthquake or war, the experts say, one normally begins by quantifying the damage, then financing the reconstruction, then setting about the task. In Lebanon, that simple formula does not work - for many reasons:
* Only the city of Beirut is ready for rebuilding. Every other area of the country, beginning at the city limits of the capital, is occupied by an armed force other than the legitimate army of the republic.
* Even Beirut's stability is untested. A diplomat here warns that there are tons of undiscovered explosives and cached weapons. Though east and west have been reunited, the diplomat says, animosities have scarcely been healed since the convulsions of last summer.
* Fighting in the countryside persists. Internecine battles rage in the southern Shouf mountains and in the northern Tripoli district. Palestinian guerrillas are active against the Israeli Army in the stretch of Lebanon from Beirut south to the border. The Bekaa Valley is under Syrian/Palestinian control and could become a battleground next year if a political settlement is not reached in time. The now-unarmed Palestinian refugees (some 600,000 in the country altogether, most in Beirut and southern Lebanon) are vulnerable.
* Damage assessments are being derived in large measure by guesswork. This is because the death and destruction go back to 1975, though they were especially intense during the Israeli invasion last summer. Recordkeeping has been marginal due to the extended duration of the conflict, the expedient of mass graves, and the destructive power of modern weapons. During that time, moreover, a degree of make-do rebuilding began in the quiet spots: Some of it survived, some was illegal and is being demolished, some was destroyed in subsequent fighting.
There are preliminary estimates of the awful toll of war in Lebanon. Seven years of civil war resulted in 100,000 deaths. Three months of fighting following the Israeli invasion caused 50,000 deaths. Cost of rebuilding is projected at $12 billion over the next five to nine years.
Who will pay for putting Lebanon back together?
Lebanon's reconstruction director, Muhammed Atallah, says his country's domestic financial markets might provide $4 billion, Arab states led by Saudi Arabia $4-$6 billion, and foreign aid and international bank loans $2-$4 billion. The United States already has pledged $110 million in emergency economic aid and is contributing to interim security and the rebuilding of the Lebanese Army.
The World Bank, meanwhile, is considering a Lebanese request for a $500 million loan. Arab League nations have promised $2 billion. And Saudi Arabia is quietly putting up considerable financial and service support.
Israel, the perpetrator of most of the recent destruction, is contributing little to the rebuilding. But Israeli officials argue that their invasion brought about the security that is allowing Lebanon to think about rebuilding today. Israeli Cabinet ministers and opposition leaders have criticized Lebanese President Amin Gemayel for failing to note this in his early speeches.
Whether or not the Israeli invasion was a violent means to a salutary end is, perhaps, a matter for historians to debate. Mr. Atallah points out that while the seven years of war before the invasion caused heavy damage ''the new damage has hurt more because it was concentrated in cities, in areas where there were not only demographic but capital concentrations.''
A number of foreign-aid teams are examining Lebanon today. Perhaps the most reliable damage estimates will come out of a World Bank study that was being conducted in November and should be completed by the new year. For its part, the Lebanese government has targeted for aid the most adversely affected sectors of the economy - housing, schools, hospitals, ports and airports, electricity, roads, telecommunications, and potable water. Housing alone will cost $700 million to rebuild, according to a preliminary government report.
Reconstruction estimates have been viewed skeptically in some quarters, however. France's aid coordinator, Alain Hatecoeur, said he had heard ''rather colossal figures'' and ''all those whom I have contacted, be they at the level of the European Economic Community or a number of international institutions, were quite surprised.'' Considering the dimensions of the need, Mr. Hatecoeur advised, experts should establish rebuilding priorities and work methodically, even though the public is eager for quick progress.
''Those . . . years of war have left the whole system disjointed,'' he says, ''be it at the level of manpower or organization. Things will not necessarily be done quickly.''
Even as damage assessors are out in the field, however, industrious Lebanese are forging ahead with rebuilding the capital and the southern cities under Israeli control. Many of the country's Palestinian refugees are being hired on construction jobs in southern Lebanon. As the projects pick up speed, economists say, unskilled labor will be in such great demand that Lebanon may have to import labor from southwest and southeast Asia.
One of the most widely praised figures in the recovery is Lebanese contractor Rafik Harrari of Sidon. Mr. Harrari, who made his fortune in Saudi Arabia's massive building program, has brought in scores of earthmovers and volunteered his company's services to clear war damage from the capital. Backed by Saudi money, Mr. Harrari's tractors are seen all over the city. A foreign-aid specialist credits the Harrari-Saudi effort with stimulating optimism and giving the Lebanese a quick feeling of accomplishment.
In this flurry of activity, the Lebanese private sector that rode out the war years is being joined today by repatriated Lebanese who had fled to Europe, Africa, and the Americas during the 1975-82 period. Moreover, much of the property in downtown west Beirut - by far the hardest hit side of the city - was owned by east Beirutis who are beginning to exhibit new interest in what had been out of their reach for so long.
Still, the cleanup job is immense. Damage to the commercial sectors of the capital and the southern cities is estimated at $387 million. More than 18,000 housing units were destroyed or damaged beyond use. Everywhere are blackened high-rises, smashed apartment blocks, and stores with gaping holes caused by artillery and aerial bombardment.
Last summer's war ravaged the grand and humble alike. The luxurious seaside Summerland Hotel - bravely built during the civil war era - endured until August 1982, when Israeli naval guns wrecked it. The miles of slap-dash shops along the coast of southern Beirut, built after the downtown souks were destroyed, survived the war only to be flattened by government bulldozers because they were illegally erected.
Most devastated of all are the sprawling Palestinian refugee camps of Beirut, Sidon, and Tyre. The first rains of the season in early November turned these camps into quagmires and forced many of the Palestinian families to shelter with neighbors. Rebuilding of the camps is a political decision that the Lebanese central government has so far refused to make; in the meantime, refugees are being housed in tent cities erected where former houses were.
Says one diplomat: ''Some of the questions we are asking ourselves at this stage are: Do you rethink some of this before you rebuild it? Do you engineer it to make it better or just rebuild it in place? How much can we count on private enterprise?''
If the peace holds, many Lebanese and foreign economists predict, west Beirut's downtown may be coming back by next spring. Even the once-posh hotel district - which, like the souks, was turned into a combat zone during the civil war - could be rejuvenated. And Beirut's mayor, Mitri Naamar, is urging that the devasted souk district be redeveloped.
Reconstruction director Atallah is confident the private sector will work speedily, but he stresses the need for foreign aid to stimulate rebuilding in the first two or three years.
''I do feel that the Lebanese have had enough (of the fighting). I agree also . . . that the private sector can by itself reconstruct the country, but it will do so once given the sign that there is security and that the public sector is a believer, too.''
Security is the key.
''If . . . the political situation does not evolve positively,'' France's Hatecoeur says, ''it would not be very easy to talk about reconstruction - especially if we found ourselves in the situation that prevailed three months ago.''
An American foreign-aid specialist concurs: ''This is not like a normal disaster. It's not like an earthquake where everything was normal and the shock occurred and then it was over with. This has lasted seven years and there are still aftershocks.''
But a concerted effort is being made to broaden the base of stability within Beirut and throughout Lebanon. The highest-level mission is that of American envoy Morris Draper. He is trying to negotiate a withdrawal of Syrian, Israeli, and Palestinian forces from Lebanon.
The Draper mission has great bearing on Lebanon's internal difficulties as well as on relations between Israel and its foes. The secondary ramifications of foreign occupation can be seen in conflicts throughout the country. Observers note that Israel is giving weapons to both warring Druze Muslims and Maronite Christians in the Shouf region. By the same token, sectarian clashes in Tripoli are related to the dominance of the PLO and Syria in that area of the country.
There are deep-rooted problems between Christians and Muslims, rightists and leftists, the rich and the poor. Already there are indications that Lebanon's rightists - who demand all 600,000 Palestinians be expelled from the country - are pressuring the refugees. Massacres in September and a recent series of bomb blasts in Palestinian camps are probably linked to this.
It seems certain then that comprehensive security in Lebanon - enough at least to reassure investors and rebuilders - will have to be conditioned on settlement of other Middle East problems, especially the Palestinian homeland problem. Though there have been some hopeful signs this fall - including President Reagan's peace plan and the PLO-Jordanian discussions on forming a confederation - major progress depends on a change of tone in Israel. And that is far from likely.
A prominent Lebanese newspaper editor puts it this way: ''Settle the problem of Lebanon and you have settled the whole Arab-Israeli problem. But if you don't settle the Arab-Israeli problem, Lebanon is still in trouble.''