H.R. finds Tracy Brand sitting in the park looking up at the Galileo statue and talks about her worries in episode 3x20 "I Know Who You Are".
Emma and Neal meet up in a park in episode 2x06 "Tallahassee".
Snart walks Valentina Vostok back to her apartment and steals her keycard in episode 1x04 "White Knights".
Maggie goes to the bus station to pick up her father and they talk while walking through the park in episode 3x03 "Far from the Tree".
The trio is kidnapped by Flynn during an altercation in front of the White House in episode 1x06 "The Watergate Tape".