This is the 13552nd most frequent Russian word.
находившегося
"Находившегося" means "who/which was located" or "who/which was present."
Here, находившийся is a past active participle describing the noun 'museum,' indicating its location in the past.
Музей, находившийся в центре города, привлекал много посетителей.
The museum, located in the city center, attracted many visitors.
In this sentence, находившемся serves as a participle that elaborates on the noun 'house,' specifying its previous position.
Он вспомнил о доме, находившемся на той улице.
He remembered the house that was located on that street.
Here, находившемся is a participle providing additional information about the park, specifying its past location close to the river.