A well balanced, bitter yet malty, clean, smooth, well-attenuated amber-colored German ale.
A bitter beer balanced by a pronounced malt richness. Fermented at cool ale temperature (60-65°F), and lagered at cold temperatures to produce a cleaner, smoother palate than is typical for most ales. Common variants include Sticke ("secret") alt, which is slightly stronger, darker, richer and more complex than typical alts. Bitterness rises up to 60 IBUs and is usually dry hopped and lagered for a longer time. Münster alt is typically lower in gravity and alcohol, sour, lighter in color (golden), and can contain a significant portion of wheat. Both Sticke alt and Münster alt should be entered in the specialty category.
Altstadt brewpubs: Zum Uerige, Im Füchschen, Schumacher, Zum Schlüssel; other examples: Diebels Alt, Schlösser Alt, Frankenheim Alt
You can view the complete style details on the BJCP website. The 2008 style guide is obsolete but there is a similar 2015 style that you can view below...