It all happened in a bewildering blur. I thought I was being mugged, but in fact I was being kissed. When my amorous assailant stood back, I saw that she was wearing a pair of cutout cardboard ears and a sign that read Eu Sou Burro — “I’m a donkey.”

She introduced herself (in Portuguese, then English) as Luisa, a freshman at Porto University. Her get-up was one part of her university initiation. Kissing complete strangers in the street was another. Discovering my nationality, she was mortified. “I’m so sorry,” she said, wiping her lipstick from my lips. “I know how much the English hate to kiss in public.”

We were standing in the middle of Rua de Santa Caterina, the bustling pedestrian-only main artery of Porto’s shopping district. Close by, Luisa’s friend, Manuela, was warbling a medley of Phil Collins songs in a voice that made passers-by wince. Farther down the street, several freshmen holding toilet paper rolls were asking for volunteers to help them with their ablutions. All in all, the city appeared to have gone slightly mad, and in the pervading atmosphere of eccentricity I fancied that I might have identified one of the reasons why the English, in particular, have had a special rapport with this place for more than 300 years.

It is a relationship proclaimed in neon every night, when the names of the port lodges — Cockburn, Taylor’s, Graham’s, Dow, Croft and Sandeman — gleam from atop the tiled roofs of Vila Nova de Gaia on the south bank of the River Douro. A daytime visit to one of these lodges is a highlight of any visit to Porto. I picked Graham’s (www.grahams-port.com) where I indulged a cursory inspection of the oak vats in which the port matures before settling down to the main business of my visit — tasting.

The more I drank the more remote I felt from the city, for despite its vital role in the local economy, port has never been a favored tipple of the Portuguese. That is not to say the inhabitants of Porto are entirely discerning in their diet. For good reason, they are known throughout the country as tripeiros — tripe-eaters. Intestines have been featured on Porto dinner plates since the early years of Portuguese global exploration, when the best meat — doused in salt — was requisitioned by the ships, leaving the landlubbers to eat offal.

Fortified with fortified wine, I set out to explore Porto by foot. With a clear head, I might have had second thoughts, for the city is built on a cluster of brutal hills, making an afternoon stroll about as subtle an exercise as a mountain trek. My first challenge was to cross the river. The double-decker Dom Luis bridge, built in 1886 by a protégé of Eiffel (who himself designed the disused railway bridge nearby), is a fearsome prospect if, like me, you have a problem with heights. Foolishly, I opted to traverse the upper level, and trod the metal walkway on quaking legs as the traffic rushed by in perilous proximity, buffeting me with slipstream. To my left, a flimsy rail was all that guarded the sheer drop.

Back on firm ground, I tested my calves and thighs against the stairways and cobbled undulations of the ilhas, shadowy alleyways that run off the main streets, wending between dilapidated townhouses. Most were painted in peeling pastel colors. A few exhibited grander pretensions, decorated with glazed-tile murals. All were topped with pitched, red-tile roofs to fend off the notoriously damp climate.

I meandered up to the ancient cathedral, which stands on an imposing spur above the river, as impregnable as a fortress. Within the cathedral’s vast nave, tour groups shuffled between two statues that celebrated Porto’s love of all things maternal: Mary the Expectant and Mary of the Milk.

As I explored the city that afternoon, I was aware of something in the air, like an audible itch. The sound of distant chanting drifted down the streets and echoed off buildings. People were drawn out of the shops, concern etched across their faces. As I approached Avenida dos Aliados, the broad avenue that leads up to the Town Hall, the chanting grew much louder. And then, quite suddenly, it was drowned out by a sound like gunfire.

No, not gunfire. I cautiously rounded the corner and faced 200 freshmen marching with bundles of empty soda cans tied to their ankles. At a given signal, they halted, the clatter ceased, and they resumed their mantra. It was helpfully translated for me by one of the sophomores: “We are ignorant beasts. We need help to go to the toilet.”

In the three days I spent in Porto, I grew used to having my itinerary disrupted by rampant students. And when they weren’t around, other circumstances obstructed my plans. Several museums, and whole districts of the city, were closed temporarily because a conference of Latin American presidents was in town.

Ultimately, Porto reflected Luisa’s kiss. Much as I liked it, it promised more than it could deliver.