Old Town is in many ways, the heart and soul of the city. It's near the Köln Dom, surrounded by "the Ring," a ring of streets, botanical space, and promenades following the path of the old city's walls. Inside the ring and along the Rhine is a vibrant scene of bars, pubs, and restaurants. While it can get crowded, Old Town is known for its hustle and overall friendly vibe.
Tours of Old Town include tours of the Cathedral, a brewpub tour (expect to drink a lot of Kölsch), or a cruise on the Rhine. However, the best way to experience Old Town is on foot. Confident travelers may want to practice their German in this area; if you do, pay attention to speakers - Kölsch is a beer, but it's also an accent, both of which being native to Cologne. In Alter Markt Square, you'll find plenty of both, as brew pubs and bars are plentiful.
Beyond the rhythm of the bars and shops are seemingly innumerable small streets and alleys that wind through the old buildings.