Toulouse is the Pink City, which is generous: the local brick runs from orange to rust and only turns properly pink when the sun is low. There was never any choice about the material. After the Great Fire of 1463 burned for days, the city's magistrates pushed builders toward brick instead of wood, and the surviving centre is almost all of it, from Romanesque basilicas to merchants' mansions paid for by a blue dye called woad. Add one of the oldest universities in Europe, founded in 1229, and you get a city of half a million people that still feels like a student town.
It is also where Airbus assembles its airliners and where Concorde first flew, in 1969, so this is one of the few cities where a Gothic church and an A380 belong in the same plan. Five days is the right length: two for the old centre and its museums, one for the aerospace sites, one for the Canal du Midi and the Cité de l'Espace, and one for a day trip to Albi. If you came for Carcassonne, the medieval walled citadel, swap it in for Albi: it is in the "more time" list below, and day five and the FAQ say how. Cassoulet, the duck-and-bean stew the whole southwest argues about, is on the table twice.
Day one is the Capitole, the market and Les Jacobins, day two the Airbus tour, Aeroscopia and the left bank of the Garonne, day three Saint-Sernin, the museums and the quays, day four the canal and the Cité de l'Espace, and day five Albi. Start on a Tuesday. The Airbus tours only run on Wednesdays and Saturdays outside school holidays, the Victor Hugo market and Les Jacobins are closed on Mondays, and Albi works best on a Saturday. Toulouse is also the gateway to the rest of the country, and to Andorra and Baqueira-Beret in the Pyrenees.