Why it looks like this

Prague is four medieval towns that grew together around a bend of the Vltava: the Old Town's maze, the Lesser Town and castle district across the river — and the New Town, which Emperor Charles IV founded in 1348 as one of medieval Europe's largest planned projects, wrapping the Old Town with wide streets and three enormous markets.

Those markets are still the city's biggest open spaces: Wenceslas Square, 750 metres long, was the Horse Market; Charles Square, once the Cattle Market, remains among Europe's largest squares. The four towns were united into one city in 1784, their seams still visible in the street pattern.