Heidelberg (35), a celebrated German city, in Baden, situated amid beautiful surroundings, on the Neckar, 13 m. SE. of Mannheim; has many interesting buildings, including ruins of a splendid 13th-century castle, but is chiefly celebrated for its flourishing university (student roll, 800; professors, 100; library, 500,000), whose professoriate has included many of the most distinguished German scholars; it was long the centre of Calvinism; its chief trade is in books, tobacco, wine, and beer.