The Mirador del Valle is the best viewpoint in Toledo, period. Cross the Río Tajo by any of the old stone bridges, climb the road on the southern bank, and suddenly the entire city is laid out before you: the Alcázar on its promontory, the cathedral tower rising above the roofline, the medieval city walls intact, the river curving around the base of the hill. It is one of the great urban panoramas in Spain.
The view is best in the late afternoon, when the light rakes across the old stone and the city glows amber. At sunrise the valley fills with mist and the city floats above it. Photographers tend to congregate at dawn and dusk; on a clear midday the light is harsh but the detail is sharpest.
The tourist train (the Trainvision from Plaza de Zocodover) stops here during its 45-minute circuit if you want to combine the view with a brief ride around the old city. On foot, it's a twenty-minute walk from the Puente de Alcántara.