I wrote about it here in
this log post. Curiosity, mental challenge, broadening my mind, discovering new things I didn't know I liked before, meeting people in different countries (and my own) who grew up differently than I did with different perspectives on life and culture.
There's also the thrill of reaching the ability to understand a language that was gibberish before. Being able to communicate with others using the language. Understanding a new culture. I still can't believe I can do this with a second language. It's like a minor miracle.
I can read in three Hebrew alphabets and understand a critically endangered language- Ladino/Djudeo-espanyol. I can break down barriers with Spanish, Kreyòl, and Kwéyòl where I live here in the Caribbean. When I have to travel to the States, Miami is my port of call gateway. Sometimes I have to stay for a day or two. I speak more Spanish there than I do in San Juan, plus Portuguese and Kreyòl. It's a wonderful feeling.
I've read books I would have never, or never could have, read in English. I've watched and listened to media not available in my native language. I've enjoyed music I wouldn't have had access to as a monolingual. I can read Pablo Neruda, García Lorca, and Pessoa in the original. I can delve into African literature with Portuguese. Languages can help me travel without ever leaving my house. I guess I just always wanted to see what was around the next bend.