If you’re from the U.S., it’s easy to think of things that date back 100 years as “old.” But overseas, that’s infantile compared to some of the structures. And these are no small outhouses or cottages — these are immense fortresses that have stood the test of time.

Some of them, you can still visit. Here are the 10 oldest castles you can still get close to and inside.

Edinburgh Castle, Scotland

Est. circa the 1180s

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This castle was built overlooking Edinburgh in the 12th century and was inhabited by a royal family until the 1600s. Afterward, it was used for military purposes and today serves as a popular tourist destination and important part of Scottish history. Make sure to buy your tickets in advance.

Dover Castle, England

Est. 1180

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This old fortress overlooks the short passage between England and the rest of Europe, making its position an important one for a castle and fortress. It was originally built in 1180 but was regularly updated with walls and towers, a lighthouse and a network of tunnels. There are a ton of tour and learning opportunities in and around this vast structure.

Killyleagh Castle, Northern Ireland

Est. 1160

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This unique castle in Northern Ireland is actually someone’s house. The original structure was built in 1160, on land given to the Hamilton family by King James I. Descendants from that family still live in the castle today, and two more recently added towers (by recently, I mean the 1600s) are available to rent out as a truly adventurous hotel. But this may not be as ancient as you anticipate — guests have use of a swimming pool and tennis courts, after all.

Alcazar of Segovia, Spain

Est. circa the 1100s

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Originally built as a fortress in the 12th century, this structure has been used as a royal palace, a state prison, an artillery college, a military academy and now, a museum. It’s another fortress that’s gone through several rounds of rebuilding over the centuries, and now it looks a lot different. But its distinctive boat shape makes it one of Spain’s most recognizable structures.

Rochester Castle, England

Est. circa the 1080s

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Another one of England’s fortresses meant to command an important water passage, it eventually included a great keep — the tallest medieval stone structure to survive in Europe. The castle withstood three attacks before eventually falling into ruin, but parts were later rebuilt and are open to visitors.

Hohensalzburg Castle, Austria

Est. 1077

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This is another castle that sits on high ground, soaring above the roofline of the city below it, and another that was built to protect royalty from attacks. The structure as we know it today was built in the 1500s, and it’s never been captured by foreign enemies. It’s open to visitors year-round, and you can see rooms and sections of the castle unchanged by time.

Windsor Castle, England

Est. 1070

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This royal residence is the oldest castle in the world that’s still inhabited. You probably know this as the place that Prince Harry married Meghan Markle, but it has an extensive history leading up to the 2018 nuptials. The original castle was built in the 11th century after William the Conqueror invaded England, and remained steadfast throughout the country’s history.

Warwick Castle, England

Est. 1068

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Also a remnant from William the Conqueror, Warwick Castle started out as a wooden fort and was gradually, exponentially, expanded. It’s where the Warwick School for boys was founded, and tourists have been checking it out since the 17th century.

Reichsburg Cochem, Germany

Est. 1,000

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This formidable building overseeing the German town Cochem was built more than 1,000 years ago and was fit for the king — but it was overrun in the 15th century by French troops in the Nine Years’ War. At that time, it was destroyed and lay in ruins before in the 19th century it was reconstructed. Today it’s open for visitors.

Citadel of Aleppo, Syria

Est. circa 3,000 B.C.

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After all of these European fortresses, the most ancient castle in the world is a palace in Syria, on Citadel Hill. The site has been occupied by many civilizations, including Roman, Byzantine, Islamic, Mongol and Ottoman empires. Remains from each one have been found on the site, but most of its current structure was thought to have originated circa 1000, with features to support residential, religious and military purposes. It was badly damaged in the relatively recent Battle of Aleppo, and restoration efforts are still underway.