Tear yourself away long enough from snorkeling and relaxing in the thermal spas of Ischia to explore this gem of a medieval fortress on a rocky islet in the Bay of Naples.
The rooftop terrace has stunning vistas of central Madrid, while the interior is a hub of the arts, from music and poetry events to lectures and science exhibits.
Alongside games of football and couples in pedalos, the art galleries, buskers and 17th-century palace give El Retiro a different flavour to your average park.
Admire the craftsmanship of the Tuscan artists and architects that created this richly ornamented bell tower. Climb its staircase for glorious views of Florence.