Here are some more places that are worth a visit when being in this region:
Wetzlar (11 km) and Weilburg (12 km): two other nice medieval cities, at the river Lahn. Also there’s a little but interesting crystal cave in Weilburg.
Solm-Oberbiel: Grube Fortuna (11 km), where you can explore a mine with a guided tour.
Greifenstein (20 km): nice castle ruins with a bell museum.
Freienfels (12 km): little castle ruins, and famous for its huge medieval festival each year around May 1st.
Favorite thing: Braunfels seems more little when you wander around the markplatz. If you see all as a body the town is more extensive, due to its architecture of little buildings and single houses.
Favorite thing: The lion of the photograph appears frequently around the Braunfels Castle. It is a figure taken from the arms of the Solms family (the city developed around the castle of the Count Solms-Braunfels).