Seville Cathedral & Giralda Tower

When Seville's chapter demolished the Almohad mosque in 1401, the (probably apocryphal, perfectly accurate) resolution was: "let us build a church so great that those who see it finished will take us for mad." They succeeded — by floor area this is the largest Gothic cathedral in the world, a forest of piers under vaults so high the eye gives up counting, with the largest altarpiece ever made (45 gilded scenes, a craftsman's whole lifetime) glowing at its heart.

Two celebrity residents anchor the visit. Columbus — or most of him; the Dominican Republic disputes custody — rides high in a bronze catafalque carried by four crowned heralds of the old Spanish kingdoms, a Victorian-era monument that manages to be both pompous and genuinely moving. And the Giralda: the mosque's 12th-century minaret, kept and crowned with a Renaissance belfry, climbed not by stairs but by 35 gentle brick ramps — built wide enough for the muezzin to ride a horse up — delivering the definitive rooftop view of orange trees, buttresses and the Alcázar's gardens below. The Patio de los Naranjos, the mosque's ablutions courtyard, survives too: orange trees in rows, the fountain still at its centre.

The skip-the-line timed ticket matters here nearly as much as at the Alcázar; the two monuments face each other and queue-share the same crowds. Strategy: cathedral at 11 after an opening-slot Alcázar, Giralda climb before the midday heat, and the rooftop-tour upgrade (small groups on the actual roofs, sold separately) if your dates allow. Evening returns are free in a sense — the exterior, floodlit, with the Giralda glowing over tapas terraces, is Seville's default postcard and costs nothing.