Madrid rewards a full week, but if you only have one day — a layover, a stopover on the way to Barcelona, or a quick side trip from Toledo — you can still hit its essentials. This route deliberately skips the smaller museums and outer neighborhoods to focus on the compact historic core where the biggest sights sit within walking distance of each other.
Start early at the Royal Palace of Madrid, arriving right at opening to tour the state rooms before the tour groups arrive, then step next door to the Almudena Cathedral. Walk through Plaza Mayor into the old town toward Puerta del Sol, the symbolic center of the city, grabbing an early lunch nearby. In the early afternoon, head to the Museo del Prado for an hour or two with its Velázquez and Goya masterpieces — skip the Reina Sofía and Thyssen-Bornemisza this time around, there simply is not room for all three. From the Prado, stroll up Calle de Alcalá to see the Puerta de Alcalá and the Cibeles Fountain and Palace. As the afternoon light softens, cross town to the Temple of Debod for panoramic views over the city. Finish the day on Gran Vía, Madrid's grand theater-lined boulevard, before winding down with tapas in La Latina, the liveliest spot for an evening bar crawl.