Headcanon: After they get together, before Lena finds out that Kara is Supergirl. She takes her on all of these vacations, eager to show the world to the woman who has given it to her. She takes Kara to the Colosseum, they kiss at the top of the Eiffel Tower in Paris (Kara eats more pastries in France than Lena thought possible) they walk hand-in-hand along the Great Wall of China. Lena also takes Kara to her favorite vineyard, and a private beach she discovered during a break from her mother.
Lena’s favorite place in the world is the cottage near Mangerton Mountain in Ireland that she purchased in cash and has never told anyone about.
It takes only one night of Lena settled between her legs in front of the fireplace, the only sounds in the world their breathing and the crackle from the fire, for Kara to decide that this might be her favorite place too. She thinks maybe her favorite place is wherever Lena is.
After Lena discovers that Kara is, in fact, Supergirl. (A misstep by Winn that Alex quickly follows with a smack to his head and various threats) Her eyes widen as the realization hits. Kara has already seen the world, probably even more so than Lena herself. When she asks Kara about it, she pulls her close and says, “Yeah, Lena, I’ve flown everywhere. But I had never really seen anywhere until I was looking through your eyes. I want to explore the rest of the world with you, see everything with you.” Kara pauses, “Can I take you to my favorite place?” The smile Lena gives her, soft and sincere, is all the answer Kara needs.
The tears Kara sees in her eyes when they land in Ireland tell her that she was right. Her favorite place is with Lena.