Ireland is a definite must. Incredible landscapes, fascinating history and culture, and amazingly friendly and welcoming people. Dublin is a great travel hub. The city itself is teeming with history and culture and is really well connected to other parts of the country via roads, rails, etc.
Dublin is surprisingly diverse with a large Nigerian and Chinese population with Polish coming in at a close fourth.
Another interesting place to visit (that most people don’t realize is an entirely separate country) is Northern Ireland (part of the UK).
Belfast is a unique city with an incredible history as well as political and social climate. Just a warning, Belfast (and the rest of Northern Ireland) isn’t exactly considered a hot tourist area (the country only recently stopped with the “troubles”). Personally I think it makes for a truly unique travel experience. You can search up more about Belfast if you are interested but if you go I highly recomend a tour of the old jail as well as the political walking tour (incredibly stories and insight to the culture and the people as well as seeing the fascinating pit stops of Belfast). Of course the country side (especially the North Antrim Coast) is just breath taking in its beauty.
One more selling point about Ireland is that it’s often overlooked by a lot of tourists in favor of the ritizer or more usual places like Italy or France so it doesn’t tend to get overwhelmingly crowded.
If Ireland isn’t your cup of tea there’s a ridiculous amount of cities and countries in Europe you can go to.
London is probably one of the most famous metropolises out there and it’s a great place to visit. The sights are amazing and the city is very accesible (the Tube is very extensive and easy to use).
Paris is arguably one of the most beautiful cities in the world. Again, so much history everywhere you look and is just filled to the brim with amazing art and fashion and incredible food. A huge selling point for me was the vast and diverse architecture from secular gothic to post modern artsy, there’s so much of Paris embodied in its buildings.
Along the lines of France, the French Riviera is a great place to vacation. But if you are a busy/impatient tourist that’s not really into the sunbathing/beach scene don’t spend too much time here.
Anywhere in Switzerland is a great place to go but I would recomend Lucerne and Zurich. Lucerne is incredibly picturesque and has some great sights to visit. If you enjoy the outdoors and are the athletic type, Lucerne serves as a hub for a ton of outdoor adventures. Mt. Pilatus and the Matterhorn are just a short ferry ride away and there’s tons of skiing and snowboarding adventures to be had in the winter.
Zurich is the complete opposite and, like London and Paris, is a metropolitan city where tons of people live and work alongside the tourists. It’s a real trendy place with, you guessed it, a lot of history and culture.
Spain is also a wonderful place to visit. Barcelona has a great mix of old and historical with new and trendy. The beach is always in sight and is crawling with things to do.
Granada is a great mix of cultures which you can see at the Alhambra (one of my favorite sights to see) as well as in the city and the people who live there.
Madrid is a bustling city not unlike Paris or London but with a style all its own. Again, the list of things to do can go on forever and ever.
If you are interested in something more Asian then Japan is a great place to visit. The culture is distinct and very unique (as most Asian countries are). Tokyo can be a little bit daunting but with a good guide book (I recomend Lonely Planet) or a knowledgable friend it can be a blast. Mega trendy and in a world on it’s own.
Hiroshima is a great place to get some history in (the WWII memorial is one of the most haunting places to visit).
China is also a good option. History and culture abound and is integrated along side daily life seemlessly. There are some great sights to be seen (the Great Wall, the Forbidden City, The Three Gorges, etc) as well as little things to be discovered on your own.
Sorry for the massive post but I figured I should share everything I’ve gone through, right? =)

You have to go to COSMEL! Its a carribean island that i’ve visited a couple times. Its so clean and beautiful! I love to sit outside my beach house and watch the sun come up. It’s the greatest thing i;ve ever seen

Crater Lake Oregon
The Oregon Caves
The Oregon Coast (all of it)
Rome Italy
Ireland (I haven’t been there, but everyone I know who has raves)
Bali
Aspen Colorado
Anywhere in France except Paris
Buenos Aires