Police believe the 14-year-old boy was allegedly sexually assaulted by the man at Echo Point Park in Sydney's north in 2023.
Heavily-armed tactical police raided a home in the affluent Sydney suburb of Killara on Thursday, seizing several electronic devices for forensic examination.
The man was led out of the home by detectives wearing a red T-shirt and track pants.
Several brown evidence bags were carried from the property by officers.
Police have been investigating the alleged sexual assault since December 2025, about two years after the alleged assault.
At the time of the alleged attack, the man was 68, police said.
AAP understands the man and teenager were not known to each other.
The man has since been charged with having sexual intercourse with a child between 14 and 16 and sexually touching a child between 10 and 16.
The 70-year-old man has also been charged with inciting a child aged between 10 and 16 to perform a sexual act to them.
He was refused bail to appear before Hornsby Local Court, and will remain behind bars until November 4.
1800 RESPECT (1800 737 732)
National Sexual Abuse and Redress Support Service 1800 211 028
Lifeline 13 11 14
Kids Helpline 1800 55 1800 (for people aged 5 to 25)
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