Wiesbaden is a short train ride from Mainz. It was founded in 6 CE and became an important spa town for the Romans. in fact, there is a fountain where the hot spring runs near the surface, called Thermalquelle Kochbrunnen.
It has been and is still known as a spa town and is one of the wealthiest in Germany. It suffered less damage during WWII and has generally been a protestant city.
Roman wall
Schloss Biebrich. I really wanted to visit this palatial house but it was closed for the season.
