Hello Michelle!

Well for adventures probably I would suggest Osa, Corcovado National Park Office. Peninsula de Osa and Drake Bay are very famous and one of my favorite spots in Costa Rica. They were declared the most biologically intense areas on earth by National Geographic as they become the premier eco-tourism destination in the country and also due to their pristine rainforests and the rugged natural beauty. However, the Caribbean side of the country is also spectacular and pretty awesome if you want adventure. I always recommend when visiting Limon: Tortuguero, Sloth Sanctuary, Almonds and Corals Hotel, Manzanillo, and Pacuare River. Google Pacuare Lodge, it is a bit expensive but they offer an entire experience of white water rafting plus lodging and an amazing culinary experience. 

Last but not least, let me recommend Mal Paisor Santa Teresa beach. They are pretty close to the Daniel Oduber International Airport. I always stay at Villas Hermosas. If you decide to visit Guanacaste in the Pacific, a must see place to visit is Monteverde Cloud Forest. If you want adventure, this is the right place as well.

My country is beautiful and Costa Ricans are unique people. I am sure you will have a blast. 

Pura vida!!

Oh my gosh, how exciting! I still think about my Costa Rica trip. Dominical is a wonderful little surfer town with delicious food and laid back people. I also went to the Corcovado National Park Office. Corcovado is definitely a drive (scary at times) but you will see sloths, monkeys, macaws and a bunch of other cool animals. We stayed at Airbnb's the entire time and it worked out perfectly. Everyone was very nice. 

I have a blog post that hits some high points. We went in December, though, so we had cooler weather. I could spend most of my time in Monteverde easily (though I'd still want to see monkeys in Manuel Antonio).

Costa Rica has something for everyone as you can imagine. So the important thing to know is what type of people are in your group and specifics are very important as niche markets for all types can be found just about anywhere worth going here. Time is also important as well as budget because this will greatly help others to know what to advise you.

For example a nature buff may be elderly and still find great tours all over the country. Middle age, young athletic or even pudgy but healthy people from all over the world can access just about every place with ease here with the transportation infrastructure.

I will list what I believe to be essential trips or adventures that I have done and can give a 5 star rating for anybody from Pregos to centenarians.

In no order:

1. Arenal Volcanoe and this region, a cool view a safe distance away can be found at the Springs Resort where there are amazing rooms and services including a fabulous wild cat sanctuary.
   
2. Heres my Canyoning and waterfall rappeling with Pure Trek
3. Mangrove Crocodile Tours with handfeeding of wild crocs
4. Visit the Produce Markets and Organic Fairs
5. Stay in a beach house that gets monkeys! Montezuma
6. Snorkel in the Pacific Ocean
7. Hula hooping with a crowd in San Jose every Saturday and Sundays is a super fun tourist highlight for the last 5 years!

Very well, I hope you enjoy these ideas and have an amazing time. note: these are personal ideas and experiences as well as personal photos, as usual!!

It's a whole country with two coasts running it's length and a lot in between. Can you narrow your question a bit or give everyone a time period to work with?