This is the 10227th most frequent Russian word.
близко
Close; near.
Here, 'близко' is used as an adverb describing the proximity in relation to the park.
Я живу близко к парку.
I live close to the park.
In this case, 'близко' indicates a short distance between two people.
Мы сидим близко друг к другу.
We are sitting close to each other.
This example uses 'близко' to describe the location of the lake in proximity to the city.