Finally destroyed after the revolution of 1868. From that times preserved arsenal building, where now is Parliament of Catalonia. Park was designed for the World Exhibition in 1888* -
From this period are buildings of the Museum of Zoology, Museum of Geology, and also - a fountain with cascades in the northern corner.
Today home for around 300 species of animals (and place of trained dolphin shows) – Zoological Park - was opened 6 years later in the eastern part of the area.
In Warsaw history with Citadel is similar. It was built during Russian Partition, by Russians, after suppression of the 1830 November Uprising. It was built by the same reasons that Philip V buit Ciutadella in Barcelona. To show the power and scare people, who might rise. You can still visit well conserved parts of Citadel in Warsaw, which also are surrounded by plenty of green.
*Ciutadella Park, Museums’ buildings, Arc de Triomf and all the mix-up caused by World Exhibition is shown as a really fascinating history by Eduardo Mendoza in ‘The City of Marvels’ – I could strongly recommend this book to everybody who enjoyed Caminar Barcelona classes.