I always love trips to Hermann. The city was founded in 1836 by the by the Deutsche Ansiedlungs-Gesellschaft zu Pennsylvania (German Settlement Society of Philadelphia). Concerned because of the English influence on their children and the loss of their German traditions and customs, the society had almost utopian goals of a "heart of German-America" wherein it could perpetuate traditional German culture and establish a self-supporting colony built around farming, commerce, and industry. Hoping to build a city that could rival Philadelphia, Hermann's Market Street is 10 feet wider than Market Street in Philadelphia.
Hermann is an easy drive from St. Louis, MO. If you are in the southern half of the city (as I am), you take I-44 west to Washington, MO, and then MO-100 to Hermann. If you are in the northen half, take I-70 to MO-19 and then into Hermann. During Oktoberfest, however, I like to take Amtrack. The station is within easy walking distance of Hermannhof Winery & Sausage, and while the scheduling isn't optimal, you don't need to worry about a designated driver when you return home. Finally, you can ride your bike along the Katy Trail; however (unless you're especially fast) you should plan on spending the night in a bed-and-breakfast.
The main reason for visiting Hermann is the wine. As mentioned, Hermannhof is right downtown and is a great place to start. Stone Hill Winery is also within the city, and while I've walked to it in my younger days, now I'd either drive or bike there. Outside the city proper (but still sharing a Hermann address) are Oak Glenn Vineyards & Winery, and Adam Puchta Winery.