Tàpies' Homenatge a Picasso (1981) is a striking public monument, in which a contemporary artist (born in Barcelona, with deep family roots in the city) salutes Picasso, who spent only a short time in Barcelona as a student but always retained an affection for the place. The essential information is on the website of the Tàpies Foundation. There is also an excellent article by Colm Toibin, who considers the work and compares the lives of the two artists.
There is probably no one key or 'answer' to a monument like this. It is better to let its many elements play on your imagination. For me, its proximity to the Parc de la Ciutadella makes it a natural episode in the story of memory and the assertion of culture over barbarism which that site represents.