It's surprisingly difficult to bicycle at 10 km/h and no more, at least on my bike with standard 700c wheels. It generally feels like if I sneeze I'll go clearly over and it's easy to drift into too fast.
(Toronto's Mt. Pleasant cemetery has an official bike speed limit of 10 km/h. One of my personal perverse acts is that when I go through it riding by myself, as I did today, I try to stick to this speed limit. It's absurdly hard to go that slow but oddly fun.)