If you love nature, if you love to be around wild animals, Galápagos is The travel destination!
I worked at the Galápagos for several years and I had the opportunity to see some of the most amazing sceneries and unique animals. The Galápagos archipielago is well protected by the Ecuadorian government and you cannot just wander around on your own. You have to travel on a licenced yacht and be accompanied by a licensed naturalist guide (that was me!)
Some of the best islands to visit are: Santa Cruz (to see giant tortoises in the wild!), Isabela (for its beautiful volcanic landscapes), Bartholomé (for its famous view and for swimming with penguins), Plaza (for all it's bird life and for swimming with sea lions), North-Seymour (for its Blue footed boobies and frigate bird with red inflated pouches).
I recommend to spend at least one week on a yacht that travels around the islands. You sleep on board and do most of the travelling at night. This way you get to see much more than when you stay in a hotel from where you make day trips. I do however, also recommend to spend a few days in Puerto Ayora, and make a trip to the highlands of Santa Cruz. This is one of the best places to see giant tortoises in the wild.
I lived for a year in the Galápagos and we actually rented a small appartment in Puerto Ayora.
Travelling to the Galápagos is not cheap (it's far away and remote) but worth al your money:
Flight $ 360
National park entrance fee $ 100
Yacht $ > 500+ (depending on luxury)
Have fun exploring!