Trip tip: always leave room for gelato.

Five days is a comfortable minimum for several neighborhoods, food and a day trip.
Cover up appropriately and follow the rules at temples, and treat offerings on the ground with care.
The train and subway network is fast, punctual and covers almost everywhere, and a rechargeable transit card makes it easy.
Be wary of friendly strangers who suggest a bar or a relative's shop, and of shoe-shiners who drop a brush for you to pick up — both are well-known setups.
Three to four days covers the tall towers and the downtown area, the older district around the creek, a beach afternoon and a desert experience.
The metro is clean and useful for the main corridor, taxis and ride-hailing apps cover the rest, and many malls and stations are linked by air-conditioned walkways.
Three to four days covers the Gothic Quarter, the main Gaudí buildings, a beach afternoon and an evening or two of late dinners.
Restaurants right beside the busiest tourist squares are aimed at passing visitors.
The metro is clean, frequent and reaches nearly every sight.
The historic tram 28 is often packed, with long lines at the start of the route and a reputation for pickpockets.
Four to five days lets you see the major landmarks, a couple of museums and a few neighborhoods without rushing.
The subway runs all day and night and is the fastest way to cover distance, and much of Manhattan is walkable.
Be careful with offers of free gifts or discounted tours in exchange for attending a resort or timeshare presentation.