La mezquita de Aljama en Córdoba, España.  The construction of  the mosque was begun by the Moorish emir Abderramon I and expanded by Abderraman II, Alkahan II and Almanzor.  It is mostly the expansion by Alkahan II that we appreciate today.  The 2400 meters squared, columns, arches, gold inscriptions from the Koran, and the mosaics are impressive.  In 1523, after the reconquest of Spain by the Christian monarchs, a church was built in the heart of the mosque.  Its Baroque altars of red marble, intricately carved mahogany chairs, for the choir, and the Cathedral's treasure all reflect the glory of the Empire.