Seville Cathedral - the world's third largest - was a mosque!

Perhaps the first place that you might want to see is Seville's famous Cathedral, near the center of the old town.

When it was completed in 1506, "Seville Cathedral supplanted Hagia Sophia (in Istanbul) as the largest cathedral in the world, a title the Byzantine church had held for nearly a thousand years. The cathedral is also the burial site of Christopher Columbus" - says Wikipedia. That was an indication of the wealth and importance of the city, built upon the riches from the Americas. Seville Cathedral's record was itself supplanted much later in that same century by the completion of St Peter's Basilica in Rome. After the passing of over 500 years, Seville Cathedral is still the world's third largest church building.

As with many other churches in Spain, Seville Cathedral was built over a grand Muslim mosque. When work started in 1402, the mosque on the site had already been standing for over 200 years.

At the cathedral, you may still see sections of the old mosque building, including the bell tower, so imposing, it has its own name, the Giralda - and you can see the distinct resemblance to the minaret of the Koutoubia Mosque, still the largest mosque in what was then the capital of the reigning Almohad Dynasty, in Marrakech, Morocco, built a few decades earlier - a reminder of their dynastic capital in their new capital of their Al-Andalus territories in Seville (Ishbiliyya) which they had just moved from Cordoba.

NO, that's not in Seville - it's the earlier Koutoubia Mosque, Marrakech, Morocco, upon which the original Seville mosque was modeled - and it's just about as tall as Seville Cathedral's surviving Giralda bell tower  
(Image Credit: Mitchell Owens via architecturaldigest.com)

Here is an interesting article by Paul Lunde that goes into the travails of how the Muslim Moors constructed the Giralda: [ http://islamic-arts.org/2012/the-giralda/ ].

That's the kind of view of the Giralda from the typical narrow lanes that is more recognizable as Seville

Seville Cathedral shows Islamic influences beside Christian symbols

Seville Cathedral - one of the side entrances