Take a boat tour around the island.

A trip to Kos isn't complete without a boat ride along the coast to discover hidden bays and strange sea caves. You can swim and snorkel in the clear water, then relax on the deck with the sun on your back and the beautiful scenery around you.
Take a trip to one of the nearby islands and spend the day there. Nisyros, Kalymnos, and Pserimos are all fun choices, with craters and villages in the mountains to explore.
Walk in ancient footsteps at Asklepieion
This legendary medical centre, named after the Greek god of healing, is one of the best things to see in Kos if you like history. Asklepieion, which dates back to the 3rd century BC, is thought to be where medicine began.
The ruins are on a hill near Kos Town, covered with pine trees. You can climb up several levels to see Roman baths and temples. On the way down, stop by the museum.
The centre seems to be built to honour Asklepios, the god of health and medicine. In the past, all doctors were priests, and people were told to pray while being treated (as anaesthetics weren't around way back when).
Now, if you go on a sunny day, bring lots of water and a hat because there isn't much shade and the sun in the Mediterranean is strong.
You can get in for about €8–€15, and you can probably spend about 1–2 hours there.
Explore a castle
The Byzantine Palaio Pyli Castle is a must-see for history buffs. It is hidden in the mountains and surrounded by pine forests. The strong fortress was built to protect the people who lived there from pirate attacks. It can be reached by a steep path that winds up the hillside. The climb to the top is worth it for the views!
Walk along the crumbling castle walls and buildings, then have a refreshing drink at the café with a great view. The Castle of Kefalos has stood the test of time. It was built in the 14th century and perched on a hill with a great view of Kefalos Bay and its nature. There's no charge.
The Antimachia Castle was built in 1457 to protect against an Ottoman attack. It is a beautiful historical building that is still in good shape. When you go inside, you can see engravings on the walls and other places to hang out that were once churches.
Neratzia Castle (Castle of Knights), which used to be on its island, is now connected to the mainland by a bridge. There are four towers inside that you can climb to see the sea and the architecture, columns, and gates inside.
Kastri Island
After all that swimming, go to the Mediterraneo Restaurant in Agios Fokas, which has some of the best seafood on the island.
Also, don't forget to book this amazing boat trip from Kos to three gorgeous islands. You'll be picked up at your hotel and taken on a trip to Nisyros Island and Panagia Spillane, which will be the highlight of your trip. You'll also have a lot of time to look around the beautiful town of Mandraki.
Just make sure you buy these tickets before you get to Kos. This way, you'll be sure to have a seat and won't have to worry about getting things set up when you get there.
Enjoy the beaches
Now, one of the best things to do in Kos has to do with its beautiful coastline, and boy, does it have a beautiful coastline.
Go to Kefalos Bay, where you can find beaches like Agios Stefanos, Kamari, and Agios Theologos. So, go to Kala Paradiso Beach or Tingaki Beach if you want to get away from most other people.
You won't know what to do first. If you can't decide, you can just get in your car and drive along the coast. I'm sure you'll find a lot of beautiful bays and hidden coves to paddle in.
City skyline
You have to wind up unpaved mountain paths to get to the top of Mount Dikaios, Kos's highest point. This is a fun way to see places tourists don't usually visit. Every corner has thick plants and big views. At the top, you can go into the small chapel of Christos and take pictures of the whole island. In a nearby village, you will have lunch at a traditional tavern.
You'll see some of the best things to do in Kos, especially when you get to the top of Mount Dikaios and eat the most delicious Greek lunch.
Birthday Sparks
You might want to go to the Castle of the Knights of Saint John after spending some time on Kos's beautiful coast. It's a beautiful part of the island that you should check out if you're touring.
From 1380 to 1514, local stones were used to build the castle. This makes it pretty old.
The castle has been around for a long time because it was built to protect itself. But don't worry, crossing the moat is easy because there is a drawbridge. Take care not to fall in.
Oh, and don't forget that the view from the top of the tower is amazing.
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During Roman rule, the Roman Odeon was built between the 2nd and 3rd centuries AD. Still, it wasn't found again until the early part of the 20th century, when there was a big dig in the area.
The original marble seats from the first nine rows of the Odeon are still there. These seats were probably only for important people.
The Odeon is in the shape of a half-circle, and it seems it once had a roof for events on the island. After walking around and seeing the ruins of the skene (the stage) and learning more about the history of this place,
If you like history, this is one of the best things to do in Kos, and the best part is that it's free.
Casa Romana
The Casa Romana, also called the Roman House, is being dug up in another area. It dates back to the 2nd century. If you like history, you'll love this place. It's also one of the best things to do in Kos if you want to learn about the Roman history of the island.
When you get here, don't forget to look at the frescoes. Just keep an eye out for the one that is so elaborately decorated and has a panther and a bear on it. Lastly, don't forget to look at the old mosaics. You'll go back a long way in time.
Hippocrates Tree
The Castle of Knights is close to the Hippocrates Tree, a must-see if you're in the area.
This huge old tree is thought to be the biggest in Europe. It is about 500 years old. It took the place of an older one that Hippocrates may have planted and used to teach his students.
Since Hippocrates lived around 500 BC, the first tree may have been replaced more than once.
Now, you'll probably only spend about 10 minutes here, but combining it with lunch at one of the nearby tavernas is a good idea.
Castle of Antimachia
After walking around the village of Antimachia, it's a good idea to also visit the nearby castle.
The Venetian Castle of Antimachia is in ruins, but that doesn't make it any less impressive, especially if you want to learn about the island's history.
A plaque on top of the main gate shows that improvements were finished in 1494. The castle was built in the early 1300s (from what I remember). Now, the castle walls are still there. Inside, you can visit two churches, but most other buildings are in worse shape. After that, if you want to go for a walk, go to the Antimachia mill and the Plaka forest. It's a lovely place.