The small town of Cognac, on the banks of the Charente river, exists largely because of the spirit that shares its name. When you arrive you can actually smell it -- the evaporation from tens of thousands of aging barrels (the "angel's share") feeds a black fungus that coats the walls of the warehouses and gives the old town a distinctive dark patina.
Most visitors come to tour the grandes maisons. Hennessy, the largest, offers guided visits of its riverside cellars and a boat crossing to its ageing warehouses on the opposite bank. Martell, the oldest house (founded 1715), and Remy Martin, which works exclusively with Grande Champagne and Petite Champagne grapes, are also open for tours and tastings. Smaller producers in the surrounding countryside often give more intimate and educational visits.
Beyond brandy, Cognac has a pleasant medieval old town along the river, a Renaissance chateau (where Francis I was born), and good walking along the Charente. The countryside around the town, particularly the Grande Champagne area to the south, is rolling vineyard land dotted with Romanesque churches -- lovely for a day of driving or cycling.