I've traveled solo for over 20 years. Here are the cities I would go back to alone, and the ones that would be better with a travel buddy.

• Travel writer and photographer Michelle Gross has been traveling solo for over 20 years.
• She's been to every continent and says Japan, Switzerland, and Vietnam are among her favorites.

The first time I traveled solo, I was 15 years old. A shy and budding tennis player, I spent two months crisscrossing Austria, Switzerland, and Germany via Eurail on a junior tennis tour.

While my dreams of going pro are behind me, that trip left an indelible mark on my life. I've spent stints living in Paris, Prague, and Istanbul and have traveled solo to countless cities and every continent in the years since — for both work and pleasure. I find traveling alone to be one of the most rewarding and empowering experiences a person can have.

As much as I love traveling alone, I'd still prefer to return to some places in a group or with a travel buddy. Here's a shortlist of some of my favorite cities I've traveled to solo, including a few I wouldn't travel solo to again.

1. Okinawa, Japan

I've traveled solo to Japan a few times over the years. From hot spring hopping in Beppu to a self-guided food tour in Osaka, I've found that getting around Japan by bus and train is incredibly safe and efficient, which is why I consider it to be an ideal solo travel destination. This year, I traveled solo for the first time to Okinawa.

Less than a two-hour flight from Tokyo, this subtropical island is a designated Blue Zone and has some of the most beautiful scenery and kindest people I've ever met. Ideal for adventure lovers and anyone interested in spirituality, history, hiking, scuba diving, and the great outdoors, I would return solo in a heartbeat because of the safety and kindness of locals here.

2. Bad Ragaz, Switzerland

Switzerland has maintained a reputation for being a safe destination for solo travelers, and after ten days circumnavigating Switzerland by train, I can confirm that reputation is true. While visiting Bad Ragaz, Switzerland I felt incredibly safe, which is always a priority to me as a solo-traveler.

Home to some of the best health spas and natural hot springs in the world, Bad Ragaz is a quiet and idyllic thermal spa town. I loved hiking around the five lakes on Mount Pizol, and I would go back alone. My stay at a traditional thermal hotel in town remains the best spa experience I've had to date.

3. Hanoi, Vietnam

I spent the better part of a summer backpacking across Southeast Asia. I'd never been to this part of the world, and I was intimidated about traveling here alone for the first time. I'm so glad I pushed through my fears.

I challenged myself in ways I never thought I would, and the experience was so rewarding. I spent the bulk of my time solo in Hanoi, Vietnam. I would spend less than a few dollars a day on meals and fell in love with Vietnamese iced coffee. In addition to the cost-effectiveness of traveling solo here, I found the locals to be incredibly welcoming.

I've traveled to Hanoi solo twice, and wouldn't hesitate to travel here again by myself. Still, no matter where I visit, I always check travel advisories and share my location services with close friends and family.

4. Phucket, Thailand

The first time I traveled to Phuket, Thailand, was on a solo trip for work. I had an amazing time practicing yoga, visiting a monkey temple, and eating delicious Thai food to my heart's content.

Phuket is a popular party and honeymoon destination, and unless I go back with my husband, some friends, or on a yoga retreat — which a good friend of mine loved — I wouldn't go back to Phuket alone. Many of the luxury beach resorts, including Sri Panwa where I stayed, caters to couples and families.

I would rather share the experience with my husband on a romantic vacation or with a group of friends to experience the island's party scene, next time.

5. Dublin, Ireland

One of my first major travel assignments landed me in Dublin, Ireland. I've traveled to Ireland before with my family and was excited to go back and experience it on my own terms. I was excited to dig into the local culture and visit places like the library at Trinity College and stroll through St. Stephens Green.

One of my favorite things about traveling solo here (or anywhere, really) is slipping into an atmospheric pub for a pint. I found people in Ireland to be extremely approachable and always keen for a chat, which is one of many reasons why I'd return to this city alone.

One afternoon, I signed up for a literary walking tour of Dublin and ended up meeting a fellow writer at a historic pub called The Palace Bar, and we've kept in touch ever since.

6. Istanbul, Turkey

I lived and worked in Istanbul, Turkey for a few months during grad school, and it remains one of the most formative experiences of my adult life. I loved my neighborhood and apartment in Beşiktaş and spent most of my weekends exploring the city and greater Turkey.

Istanbul has changed considerably in the years since I lived there, and while I would consider traveling solo to Istanbul again, I wouldn't travel around the country as liberally by myself due to ongoing safety issues.

7. Tel Aviv, Israel

The first time I traveled to Israel, I was solo, single, and in my mid-20s. I ended up meeting some of my closest friends to date on this trip, including a good friend who lives and works as a tour guide in Tel Aviv.

An incredibly vibrant city, Tel Aviv's art scene, restaurants, and nightlife is second to none, and while I found it safe to walk around and explore, it's a city that I think is much more enjoyable in the company of friends.

Uber's weren't reliable and taxis getting around town were expensive. Because of the high costs of transportation, and since it's more fun going out and experiencing the nightlife with friends anyway, I'd rather return to Tel Aviv with a group.

8. Port Douglas, Australia

One of the coolest towns I've ever been to, Port Douglas in Queensland, Australia, blends lush rainforest, beautiful beaches, laid-back restaurants, and waterfront bars all into one. The town is best known for being a jumping-off point for the Great Barrier Reef, and while I loved my solo visit, I wouldn't go back alone.

Port Douglas was a place that really won my heart thanks to its abundance of natural beauty. It's a place that has so many cool things to do, but I would want to share it with a travel companion next time. There's a restaurant tucked away in the jungle in Port Douglas where everyone from Mick Jagger to David Bowie has been to, and it's far too special of a place not to share with my husband if I ever go back.