They are for the most part treasured in the most important museums of Europe and America, Sozain.
If you google The Garden of Earthly Delights (the wonderful painting that motivated this thread), for example, you will see it is in the Museo del Prado in Madrid, Spain (Wikipedia).
And so on, so forth for any other famous artworks. An interesting search indeed.
I always saying again and again it is very great painting. And I always ask where are these painting right now.