On warm spring nights, the bridge is the place to be for courting couples in the capital of the most populous Arab country, where poverty, crowds and a conservative culture leave few other meeting places.
"We know how to be in love in a place like this," says Ibrahim, 19, a student and part-time DJ in Cairo. "We come for the breeze, the view, and to be far from the pollution," he said, resting on the bridge's iron railing with his fiancee, Marwa, an 18-year-old technology student.
The high cost of getting married -- from gold jewellery for the bride to the ceremony itself and a place to live -- and the poverty of many residents of Cairo, means engagements can last years.
On Thursday nights on the eve of the Muslim weekend, couples line the bridge, each pair a few meters apart. They face outward to enjoy the view and avoid being seen by relatives.
Yachts and motorboats ply the Nile below -- a one-hour ride can cost as little as 5 Egyptian pounds ($0.95), and vendors offer flowers for a pound apiece.
A giant fountain sprays a plume of water high in the air where two branches of the Nile meet at the end of an island lined with palm trees.
"We have so many memories from being together here," said Eman, 19, who comes once or twice a week to meet her fiancee Bahr, 21, also a student.
The two met at Eman's house two years ago under the kind of close family supervision that often surrounds engagement in Egypt, said Eman, her bright yellow headscarf fluttering in the warm breeze.
Almost all Egyptians live with their families until marriage, and the country's traditions make it difficult for couples to meet in seclusion.
Meetings on the Nile bridges are a chance to be together away from parental oversight. Social codes that frown on public displays of affection, such as holding hands, are often overlooked on the bridges.
"We can't go to any place where the family can see us," says Mohammed, 26, an engineering student at Cairo University. "You can take your sweetheart to a bridge, look at her, and forget about the street behind."
Many young people also have difficulty paying for coffee in a cafe or going to the cinema. Inflation, at a three-year high of 14.4 percent in the year to March, hits the poor hardest.
Despite Egypt's rapid economic growth, helped by flows of petrodollars from nearby Gulf Arab countries, the proportion of people living in poverty has risen. About a fifth of Egypt's roughly 75 million people live on less than $1 per day, the United Nations said in October.
Many men have to wait until well into their 30s to save the money they need to buy a place to live and get married.
"Marriage is costly and with the economic conditions such as unemployment and low salaries, it gets delayed," said Madiha el-Safty, a sociology professor at the American University in Cairo. "Social problems result. There is a lot of frustration among the young when they cannot get married."
Unmarried and without a home of their own, many of them come to Qasr el-Nil bridge.
"No one can get married in this country," says Ragab, 24, who has been engaged for a year. "The families of the women are so demanding. They want an apartment, furniture and gold."
Ragab estimates he would need to save at least 25,000 Egyptian pounds ($4,500) to pay for a wedding and for the traditional "shabka" jewellery gift the groom must present to the bride.
The cost of the shabka can range from $600, for a wedding band and two bangles, to $8,000 or more for an entire set of gold jewellery and a diamond ring. Financial hardship and the high price of gold have forced poor bridegrooms to rent the gold jewellery for the wedding.
"We come here to unwind and smell a bit of the wind," Ragab said of Qasr el-Nil, which means "Palace of the Nile" in Arabic.
Ahmed Amin, 28, says he makes 1,000 pounds ($180) in a good month doing odd jobs around Cairo, which makes saving for the shabka nearly impossible.
"We've been engaged for three years and it's come to nothing," said Amin, from the south Egyptian city of Aswan.
He was walking arm-in-arm down the bridge's sidewalk with a young woman in a red headscarf, whose name he would not give.
"The Nile is the soul of Egypt," he said. "Whoever loves his sweetheart has to bring her here."