There are several mistakes. You have to work on grammar because as a native I hardly understood some of your sentences.
"Le jet d'eau est l'emblème de la ville de Genève. Il est situé sur le lac Léman, il est visible dans toute la ville. (I don't understand what you tried to say here :/). Ce jet d'eau est très apprécié des touristes.
- Be careful "ville" et "rivière" are feminine words.
- In French one doesn't say "rivière" along with the river name, just write "le Rhône" for "the Rhone river" with a capital R because it is a proper noun.
- When "le" or "la" are followed by a vowel they became "l'" so write "l'air" (same for "de" → "d'" and "du" → "de l'" (this one is itself the contraction of "de" followed by "le"))
- On the other hand "ce" is the default before masculine words that start with a consonant and "cet" is only used when the word starts with a vowel. For feminine words "cette" is used whatever the next letter is.
- I had to change the sentences of your sentences because they have structures that are not used in French.
- I used "apprécié" because you can't go into the jet and that is basically what "visiter" means.
- "plus" is a comparative word, you cannot say "Il est plus grand." but you can say "Il est plus grand que toi.". Maybe what you tried to say was "Ce jet est l'attraction la plus visitée par les touristes.". Here "la plus" (feminine) or "le plus" (masculine) are superlatives (just like "the most").
More advanced tips :
"Il est situé dans le lac de geneve et deboucher dans le riviere rhone, est visible en tout le ville et le air, inclus voler sur plus de 10km." contains three parts. It is not an error but there are two things that would surprise a native : first you use three different verbs but you don't repeat the pronoun. A French speaker would either use one verb and not repeat it or use three subjects. Second you don't use "et" for the last part, this is a bit weird because it looks like the sentence isn't finished. There are two examples more idiomatic : "Paris est vaste, polluée et surpeuplée." "Je suis jeune, j'aime le sport et je vis en France."
Hope I helped