In Amsterdam there is a famously strong one, best in Europe (while nothing compared to the Valley). Berlin is also a nice place in this respect, i know a few guys in Eastern Europe who worked in startups there. Berlin is a very unusual city because while being a capital of one of topmost tech countries in the world, it enjoys cheap rent and cost of living/doing business (because it's not overcrowded yet, legacy of the separation era, quite opposite to say, London).