The Dam square in the centre of Amsterdam has extremely bumpy cobblestones. It's not impossible to bike on, but even for bikes it's more comfortable if you go a

The Dam square in the centre of Amsterdam has extremely bumpy cobblestones. It's not impossible to bike on, but even for bikes it's more comfortable if you go a bit slower than usual, which might be the intention. The lines between the lanes are made from much smoother stone though, so when I'm in a hurry, I just ride on those lines.