In Krems, which is a very nice town and a destination for many tourists in Lower Austria, which is one of the nine states of Austria, is a monastery named Und1. It has a website, a wikipedia article and you can find it on Google Maps.
In Hungary, less than 1 km from the Austrian border, is a small village called Und2. It also has a website, an entry in Wikipedia and of corse you can find it also in Google Maps.
These places are less than 100 km apart from each other, so you could imagine a bus driving to these two places and to some others. So the bus company could print a sign with a text like this:
Der Bus nach Spitz und Und und Und und Bük fährt täglich um 10:25 Uhr vom Linzer Busbahnhof ab.
The bus to Spitz and Und and Und and Bük departs daily at 10:25 from Linz bus station.
Now you have already 5 instances of und in a row. But now let's talk about the distances between the words on that sign:
Die Abstände zwischen Spitz und und und und und Und und Und und und und und und Und und Und und und und und und Bük sind zu klein.
The distances between Spitz and und and und and Und and Und and und and und and Und and Und and und and und and Bük are too small.
This is very absurd and confusing, but still a valid German sentence that contains 21 instances of und in a row. If you read this sentence aloud, all 21 instances sound the same, and if you print it in uppercase without italics, they all look the same.
1 The name of the monastery Und comes from Santa Maria ad undas which means Holy Mary at the waves. When the monastery way build it was built at the bank of the river Danube. (The riverbed was later moved due to the regulation of the Danube and is now a few hundred meters away from the monastery.)
2 The village is named after a person who lived there in the 13th century. At that time the name of the person and the village was written Vnd. (The letter U evolved from the letter V in Latin script.)