Nicaragua
The largest most pristine rain forest in Central America.
Take a boat from San Carlos and journey a few hours down the river, stay at on of the riverside lodges.
The wildlife is too diverse to list in full but you'll almost certainly see monkeys, sloths, crocodiles, caimans and perhaps manatees.
It's a lovely tin roofed village stuck to the base of the best preserved colonial fort about a third way down the river San Juan. You can organise boat trips into the surrounding rain forest and there is an attractive (but very simple) eco-hotel in the village. Solentiname is a group of islands in the lake, near San Carlos. Fabulous painters and artisans and glorious setting.