If you want to know Germany's history better, then the best place than Mainz is simply impossible to come up with. Why? Yes, just because it is one of the oldest cities in the country. There are many monuments of history that not only reached the present day, but also preserved perfectly.
Planning a trip to Mainz, I advise you to allocate July and August, since it is these two year old months, are considered the warmest. My wife and We were here in May and I will tell you, the weather was somewhat damp, it was possible to walk only during the daytime, in the evening it was Zyabko in the evening.
Move around the city, you can both by public transport in the form of a bus and a bike that can be rented without any problems. I am a big lover of hiking, and my beloved to no avail struggles with overweight, so we basically went on foot. A couple of times, drove on the bus. A bus ticket is worth two and a half euros for one trip, but you can buy for five euros, the right to ride public transport all day.
Every year at the end of August and at the very beginning of September, the festival of wine is held here and my husband and I want to visit it next year. About security. The city is completely calm and even if you wander through its streets in full solitude, with the eye on the sides, then you absolutely threaten nothing. I at least did not hear any of the local, or from tourists about the cases of theft or a discrepanity, probably because in Germany a very low level of crime and rather strict laws about this.