Downtown Frederick is great for walking around! There are tons of shops, restaurants, and breweries. Check out Carroll Creek park (along the creek) and shop along North Market street.
Harpers Ferry is about 30 minutes away. Go there for hiking, river tubing, and breweries.
Sugarloaf mountain is about 30 minutes away.
There are lots of vineyards nearby including Links Bridge, Hidden Hills, Mazzaroth, and Orchid Cellar.