Arenal would probably be the best volcano from below. If you’re more interested in the crater, Irazu is the tallest for views on a clear day but I personally think Poas is the prettiest (and close to the San Jose/Alajuela airport, if that’s where you fly in/out). As for beaches, I recommend Playa Rosada (because of it’s pink sand), Manuel Antonio (gorgeous with animals, but a bit touristy) or Carrillo (my personal favorite because it’s sparce and pleasant). All are in the east gulf of Nicoya. Best of luck.

For diving, the north is much better, Try Playa de Coco area, great dives out to Catalina and Bat Islands. Giant Manta you can actually ride on, also a great shark dive if you like sharks. From there you can drive to Arenal,through the rain forest, we stopped for awhile to listen to the streams and the call of birds, awesome. You will pass Tabico Hot Springs area. We spent the night at the Arenal Lodge. We could see the Volcano from our room at night and the flow of lava. We climbed up part way. There is a road that takes you back to San Jose, over the mountains. It looked as if they were growing tropical plants for exportation, millions of house plants. We thought we were lost for awhile, the road became hard to follow. Actually we weren’t lost, just not familiar. We had a rent a car, and it was an adventure. Explore and have a great time.

Claire

I would definitely head to Corcovado National Park on the Osa Peninsula. It is still one of the most remote regions, which National Geographic calls “the most biologically intense place on earth”. And though I didn’t dive there, I met people who did, and thought it was incredible. But what I saw above ground was beautiful. But be aware that you must make reservations to enter the park, as space is limited.

Have fun!

I definitely endorse Corcovado on the Osa Peninsula. Unbelievable remote white sand beaches (very rough surf), and incredible unspoiled jungle hiking, bird and animal watching, etc.

Do not miss the Tabacon Hot Springs. They are incredible and you can stop in for just a couple hours.

i loved domincal/domincalita on the pacific side south of Jaco. Super tiny, secluded beaches where the locals are tight and everyone just surfs. great. and great food there too.