This is a huge novel, very densely written. The first four pages recount the ice age in vivid terms, and thus make it clear that this is one of those novels and you have to dedicate all your attention to if you want the payoff.
Dig in, settle down, concentrate.
The story is built up around a real event, when the Portugese tried to bring a Rhinoceros to Pope Leo X (this is set in the 16th century) by boat, unsuccessfully (boat and rhinoceros at the bottom of the sea). There's a good dose of Gabriel Garcia Marquez here, erudite, fantastical writing on top of a Simplicissimus
kinda of framework. The main character is Niklot, born on an island in the Baltic Sea, who survives early trauma and goes off wandering. There's a city that sank beneath the North Sea with treasure to be recovered, animal sacrifice in Roman churches, and fine goings-on in the West African rain forest.
Not for the faint of heart, this novel.