Belgium is small and dense: Brussels, Bruges, Ghent and Antwerp are all within an hour or so of each other by train, which makes day trips from a single base the standard approach. The country splits linguistically between Dutch-speaking Flanders in the north and French-speaking Wallonia in the south, and the historic Flemish cities carry most of the medieval architecture.
The guides here cover Brussels, Bruges, Ghent, Antwerp and a countrywide overview. Bruges absorbs the heaviest day-tripper traffic, and staying overnight is the simplest way to see the center without the midday crowd. Museums commonly close on Mondays, and the weather rewards flexible planning more than a fixed season — rain is possible year-round, and much of what is worth seeing is indoors.