Any people from Munich that can help me? What is on in Munich September 1st??

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I am going to travel to Munich (München) in early September for my holiday. I am going there from Heidelberg, and will get to Munich on September 1st. However, when I look for hotels, there are very few hotels available on September 1st and 2nd, and I can only find a few that has any rooms available. I found one hotel and they charged 185€ per night for the night of the 1st and the 2nd of September, whereas the night of the 3rd only was 65€. It seems something must be going on in Munich in early September causing all the hotels to be fully booked and the prices to be really high. I have tried to search for events and celebrations, but I cannot find anything? Can anyone help me and tell me what is going on? It might be something that would be interesting to know and participate in! Also does anyone have a suggestion where to stay. I booked at a hotel in the city Centre just so I'd get anything, but that can be cancelled! Any ideas will be greatly appreciated! Thanks!