Learn German: Diesseits des Sees gibt es viele Blumen. - On this side of the lake, there are many flowers.

The preposition diesseits (on this side of) requires the genitive case. Since See (lake) is a masculine noun, the definite article becomes des and we add an -s to the end of the noun, making it des Sees.

I thought See was a feminine noun. Why is it treated as masculine here?

The word See changes its meaning based on its gender! Der See (masculine) means the lake, which fits this sentence perfectly. Die See (feminine) means the sea or the ocean. If we were standing on the coast, the genitive phrase would be diesseits der See.

Why is the word order gibt es instead of es gibt?

This is a great refresher for the verb-second rule in German. The entire prepositional phrase Diesseits des Sees takes up the first position in the sentence. Therefore, the verb gibt must take the second position, pushing the subject es into the third position.

Could I just say auf dieser Seite des Sees instead of using diesseits?

Yes, auf dieser Seite des Sees is perfectly correct and means the exact same thing. However, diesseits is a concise, elegant preposition that you will encounter frequently in written German, the news, and higher-level speech.