Yes, just over the border. I live really close to the German border and you instantly notice, everything suddenly looks, well.. German.
A lot of things don't cross-pollinate because they are decided on a national level. So things like the style of signage, traffic lights and other 'street furniture' are all different. Germany also still uses a lot of above-ground cabling which is another instantly obvious difference. Building codes are probably different too, which affects how buildings look.
It's not just the country, it's the people too. Living in a city near the German border we get a lot of people from Germany shopping on weekends. Often you can spot the Germans simply by how they are dressed, especially older people. I can't really put my finger on what is different (as an IT guy I'm kind of oblivious to fashion) but there must be some subtle differences as even I subconsciously pick it up.
> Plus aren't there streets where one half is Dutch, the other half Belgian?
It's even easier to spot when you're crossed the border into Belgium, if you suddenly feel like you're driving off-road you're in Belgium.