Learn Croatian: Pored toplica je velika šuma. - Next to the spa is a large forest.

The base word for "spa" or "thermal baths" is toplice, which is a noun that only has a plural form (like "scissors" in English). The preposition pored (next to) requires the following noun to be in the genitive case. The genitive plural form of toplice is toplica.

Since the spa is plural, why does the sentence use the singular verb je?

The verb must agree with the subject of the sentence, which is velika šuma (a large forest), not the spa. Because velika šuma is feminine singular, the verb is the singular je. The phrase pored toplica simply tells us where the forest is located.

Is there a specific reason the sentence starts with Pored toplica instead of the subject?

While you could say Velika šuma je pored toplica, starting with the location is a very natural way to introduce new information in Croatian. It sets the scene first, placing the emphasis on what is located there by putting the subject at the end of the sentence.

Could I use a different preposition instead of pored?

Yes, kraj and pokraj are very common alternatives that mean the exact same thing in this context. Just like pored, they both require the genitive case, so you would say kraj toplica or pokraj toplica.