Food
Universally understood. Sustenance, source of nourishment, pleasure, comfort, discomfort. The central part of a meal.
Food brings people together. It is an interface for communication. You might not understand the words a person is saying, but you can taste it through their food.
I don’t understand Korean or Nahuatl (actually, avocado, chipotle, tomato, chocolate, chayote, peyote all come from Nahuatl), but I understand the care and love they put into the food they have decided to make for me.
Food can also be a way of literally learning another language. For me, a way to becoming familiar with basic Spanish involved learning the names of some fruits and vegetables, going to the veg shop, and asking around. ¿Cómo se llama? (holding up a berenjena).
In Spain, a lot of pride is taken in the display of vegetables and fruits (actually, the display of anything, even the screw shops and light bulb shops have extraordinary displays). So my interest in a shopkeepers vegetables and their immaculate display seemed to be rather inductive to conversation.