Learn Turkish: Maymunların havuzda serinliyor olması oldukça ilginç. - It is quite interesting that the monkeys are cooling down in the pool.

Using the continuous verb serinliyor followed by the verbal noun olması emphasizes that the action is happening right now. It translates to 'the fact that they are currently cooling down.' A standard verbal noun like serinlemeleri would just mean 'their cooling down' in a general or timeless sense. This formula is how you build a continuous nominal clause in Turkish.

Since maymunların (the monkeys) is plural, why does the clause end with the singular possessive olması rather than olmaları?

In Turkish, when the subject is plural but non-human (like animals, plants, or objects), the verb or verbal noun usually takes the 3rd person singular suffix. While olmaları wouldn't be strictly wrong, olması is the standard and more natural choice for non-human subjects.

Does the word oldukça function as a verbal adverb here, using the -dıkça suffix?

Not anymore! While it originally evolved from the verb olmak (to be) plus the suffix -dıkça ('as it becomes'), oldukça has become a fixed dictionary word. Here, it simply acts as an adverb of degree meaning 'quite' or 'rather', modifying the adjective ilginç.

Where is the main verb in this sentence?