The new Canon 16-35mm f/4L IS is a new, much sharper lens than the 2.8L II in the corners. If you don't require the low-light performance of a f/2.8 lens, the 16-35mm f/4 IS offers lower distortion and better resolution at the edges than its f/2.8 counterpart. The optical image stabilization helps compensate for the high minimum aperture when shooting in low-light. The lens is best used in landscapes and other shots that require expansive compositions in bright light.
Other options include 16-35mm f/2.8L II for low light performance, the Canon 14mm f/2.8L II ultra-wide for even wider photos, and the Canon 15mm f/2.8 Fisheye to enhance the feeling of movement.