Kilometre Zero of Spain, and the neighbourhood most first-time visitors never leave — for both good and less-good reasons.
Puerta del Sol itself, the official centre of Spain and starting point for all national road distances; Plaza Mayor, the grand 17th-century arcaded square a few minutes' walk away; and the Palacio Real just beyond that. This is Madrid at its most postcard-familiar.
Busy — genuinely the busiest part of the city, day and night. That brings energy but also the highest concentration of tourist-priced restaurants and the occasional street hustle common to any capital's central square. Walk two streets off the main squares and prices and atmosphere both improve.
First-timers on a short trip who want everything within walking distance, and don't mind trading some local character and a bit of noise for pure convenience. Less ideal for a longer stay or for travellers who prioritise a quieter base.
For food, walk toward Calle de la Cava Baja in neighbouring La Latina rather than eating directly on Plaza Mayor — the square's own restaurants are priced for footfall, not for quality.
Sol is a major Metro interchange (three lines cross here), making it one of the best-connected bases in the city regardless of where else you're headed.