In Africa, in the country of Nanibia is the Otossia National Park. It's the best place in the world to go on Safari. It's in a salt pan, so there's very little vegetation, very few water holes, so the animals all congregate in those places and they're easy to see.
For Asia, I would recommend trekking in the Annapurna Himalayas. You can see some incredible views. It's very good exercise. The people are friendly and it's very cheap and safe to do. And Annapurna is in Nepal in case you don't know.
In the region of the Pacific Islands and such I would recommend going to the Great Barrier Reef off the East Coast of Australia, especially if you enjoy water sports and things like scuba diving and snorkelling. It's a very good place to go. It's safe and clean and you can see an incredible underwater world.
For South America, in the country of Bolivia, you can go to the Uyuni Region. You'll never see a sky so bright. The sun is reflecting off the surface of the salt pan which has a very thin layer of water.
In Central America, I would recommend going to Tical in Guatamala. It's a Mayan ruin which was only discovered more recently than some of the older ones so it's still in very good condition and it's still in the Jungle setting, so you will have Howler monkeys in the trees and lush vegetation around as you walk between temples.
In Europe, I really like the city of Barcelona. It has a very lively atmosphere. There's a lot of culture and arts everywhere. It's a very fun place to spend some time if you enjoy art and nightlife and vibrant culture.