Learn Dutch: Er is een park in de stad. - There is a park in the city.

Just like in English, when you want to point out that something exists, you use er is (there is) for singular nouns and er zijn (there are) for plurals. Since een park is singular, we use er is.

What happens if I want to start the sentence with the location?

Dutch uses a strict rule where the verb must be the second part of the sentence. If you move in de stad to the front, the verb is must come right after it, swapping places with er: In de stad is er een park.

How do I know whether to pronounce een as "uhn" or "ayn"?

Because een means "a" (a park) in this sentence, it gets a short, relaxed "uhn" sound. You only use the long "ayn" sound when you are specifically emphasizing the number one, which is often written with accents as één.

Why is it de stad and not het stad?

Nouns in Dutch use either de or het for "the". Because stad is a "de-word", we use de. There are very few rules for this, so it is best to memorize the word as de stad from the start!