Campari

The red bitter that holds up the Negroni. Campari goes back to Gaspare Campari's café in Novara in the 1860s, and it is far more bitter than Aperol, with a grapefruit-pith edge and 24% alcohol in the US bottling. Gin, sweet vermouth and Campari make the Negroni; trade the gin for soda water and you have the Americano, the better pick on a warm afternoon. Campari and soda is so simple that the company has sold it premixed since 1932, in little cone-shaped bottles designed by Fortunato Depero. Even if you only ever make one drink with it, keep a bottle: it is the bitter every other aperitivo bottle gets measured against.