Costa Rica is one of the few countries outside Europe I've visited twice. My first trip was to meet friends, and the second time I took a bit more time to explore the country at a more leisurely pace. Both times, I traveled by rental car on a road trip, which I consider the best way to explore the country. The distances are manageable, and you can easily combine different natural areas.
For me, Costa Rica is synonymous with wildlife and biodiversity. I saw Arenal Volcano spewing lava, came face to face with sloths, and witnessed turtles laying their eggs in Tortuguero. At the same time, I noticed how the country has developed and become more touristy, resulting in higher prices. Yet, Costa Rica remains one of the most accessible and impressive nature destinations in Central America.