If you're on the Blue or Green starts, there's a slight incline just after 1 mile, then a downhill thro' mile 3. If you're on the Red start, there's a fairly steep but short down/up after mile 2, before the downhill thro' mile 3 after the starts merge. There are no other significant hills, just short rises/falls of which there are several - entering Surrey Quays around mile 9, down into an underground roundabout at mile 15, a slight incline around 17 miles, another slight incline into/out of the Canary Wharf complex, then that's about it.