I'm an old Niven junky. Shame he's too old, and seemingly infirm, to still be writing. (In the back of "Burning Tower", Jerry Pournelle talks about visiting the Grand Canyon with Larry, and having to get Larry's wheelchair down the canyon.)
Try Alastair Reynold's "Revelation Space". If you like that, then the rest of that arc, and all of Reynold's other books.
Ken MacLeod's "Engines of Light" trilogy, for some more euro-centric stuff.
"Permutation City" and "Diaspora" by Greg Egan, for hard-tech mind-stretching.