Visito la fiera vicino al fiume.

In Italian, the simple present tense (indicative) covers both habitual actions and actions happening right now. You don’t need a special continuous form unless you want to stress “right at this moment.”
• Visito la fiera = “I visit the fair” or “I am visiting the fair.”
• If you really want the English-style progressive, use sto + gerund: Sto visitando la fiera.

Vicino is an adjective meaning “near” or “close.” When you use it with a noun, it must be followed by the preposition a. In Italian:
• vicino a + il fiume → vicino al fiume
Here a + il contracts to al, as happens with many prepositions + definite articles (e.g. di + il → del, su + i → sui).

Italian normally requires an article with singular, countable nouns.
• La fiera refers to a specific fair.
• If you mean “a fair” in general, you’d say una fiera.
You cannot drop the article altogether (Visito fiera is ungrammatical). English often omits articles, but Italian does not in these cases.

Some patterns exist, but they’re not 100% reliable:
• Nouns ending in -a are usually feminine (fiera, casa, porta).
• Nouns ending in -o are usually masculine (tavolo, libro).
• Nouns ending in -e (like fiume) can be either; you have to memorize their gender or check a dictionary. Always learn new nouns with their article (il/la/un/una).

Italian word order is quite flexible. The neutral order is Subject–Verb–Object + complement:
• Visito la fiera vicino al fiume
If you want to emphasize location, you can front the phrase:
• Vicino al fiume visito la fiera.
This is stylistically possible, especially in written or poetic contexts.

Depending on nuance, you might say:
• Vado a visitare la fiera – I’m going to visit the fair (focus on going).
• Sto visitando la fiera – I’m visiting the fair (emphasizes ongoing action).
• Esploro la fiera – I explore the fair (focus on exploring).
• Partecipare a una fiera – to attend a fair (participate).

Yes! Italian offers several terms:
• Mostra – exhibition (often cultural or art-related).
• Salone – large trade fair (e.g. Salone del Mobile).
• Sagra – local festival, usually food-focused.
Use the word that best fits the context.

Since fiera is feminine singular, you use the pronoun la and place it before the verb:
• La visito vicino al fiume.
= “I visit it (the fair) near the river.”