Day one: from Jardín de la Unión up to the Alhóndiga and San Roque
Start at Jardín de la Unión, the tree-shaded plaza beside the Teatro Juárez, and walk five minutes uphill along Calle Sopeña to the Alhóndiga de Granaditas. The former granary is now a regional museum with murals and pre-Hispanic and colonial collections; allow 60 to 90 minutes, and note that most museums in the city close on Mondays. From the Alhóndiga, follow Calle Mendizábal back down, then thread through the narrow lanes around the Templo de San Roque, where the callejones begin to give the city its reputation. The gradients are gentle here, maybe 200 metres of ascent across the morning, so it is a sensible warm-up before the big climb later.
Around San Roque the streets narrow to single-file width, with steps cut into the slope and houses painted in faded greens and rust reds. Break for a long lunch near Plaza San Fernando, where set menus of comida corrida are the norm and cheaper than the terrace restaurants on Jardín de la Unión. In the afternoon, walk west to the Templo de San Diego and the adjacent Plazuela, then browse the small galleries on Calle Positos. Do not attempt to drive between these stops; the one-way system and tunnels add ten minutes for every five minutes of walking. Book a hotel in the Centro Histórico so the whole day stays on foot.
The callejones: Callejón del Beso and the ones worth your time
Callejón del Beso is the famous one: two balconies almost touching above a 68-centimetre-wide passage, a legend attached, and a queue most afternoons. Entry is usually a small charge collected by the family who live there, and 15 minutes is enough. It sits just off Calle del Campanero, about ten minutes uphill from the Alhóndiga. My advice is to go early, before 10:00, or to skip it entirely and spend the time on the quieter lanes north of the Teatro Principal, where you can look up at the same architecture without waiting your turn.
Better value for the effort are the lanes on the way to the Presa de la Olla. Follow Calle del Paseo de la Presa east from the centre, roughly 25 minutes on foot, and you reach the reservoir with its dam, paddle boats and a shaded avenue. In the streets between the centre and the Presa — Calle del Cedro and the stepped lanes climbing off it — the callejones carry no legend and no crowd, and the views over the domes and the yellow Basílica de Nuestra Señora de Guanajuato are the ones you came for. Wear shoes with grip; polished cobbles after rain are genuinely slippery.
Day two: the university, the miradores and the funicular
Begin at the Basílica de Nuestra Señora de Guanajuato on Plaza de la Paz, then walk uphill past the University of Guanajuato's main building, whose long flight of steps is the city's unofficial meeting point. Continue to the Templo de la Compañía, then take Calle del Pocitos towards the Pípila monument. The climb is steep, about 20 to 30 minutes of continuous ascent with staircases, and it is the hardest part of the two days. If you would rather save your legs, the funicular from behind the Teatro Juárez runs up the hillside in a couple of minutes, though the walk down is much easier than the walk up.
The Pípila statue delivers the classic panorama of the city's alleys, domes and hillsides; go mid-morning for clearer light and fewer people. Then descend through the lanes of the Embajadoras neighbourhood, quieter and residential, with small cafés and bakeries, and a useful half-hour loop if you still have energy. Save an hour later for the Museo Casa Diego Rivera on Calle Positos, where admission is modest and the collection includes sketches by the painter born in that house. Two full days of this walking is realistic for most travellers; three if you want a day trip to the mummies museum outside the centre or to Valenciana's church, both interesting, neither essential.
Where to stay and when to go
The Centro Histórico, the streets between Jardín de la Unión and the Alhóndiga, is where I would book. You pay for the convenience, and rates climb at weekends when Mexican city-breakers arrive from León and Mexico City. The quieter alternative is the area around the Presa de la Olla, cheaper for the same standards and a 25-minute walk or short taxi from the centre. Avoid booking on the steep lanes immediately below the Pípila unless you enjoy carrying luggage up stairs; some streets there are pedestrian-only and taxis stop several blocks away.
March to May is dry and bright, with warm days and cool evenings; the rainy season from June to September brings afternoon downpours that make the callejones slick and the stairs slow going. The city's big cultural dates fill hotels fast and push rates up, so check the calendar before fixing dates. If you are arriving from Mexico City, the drive is around four and a half hours on the toll highways, or you can fly into Del Bajío airport near León, roughly 45 minutes away. A hotel booking in Centro, made early, is the single most useful decision for this plan.