While there is no exact figure for how many there are in the world, many estimates say that there's at least 1 million still standing. This number also doesn't include ruins or that are no longer with us. However, when it comes to the oldest and the largest uninhabited castle in the world, that's easy to pinpoint - and it's just outside of .

, located in Berkshire, has been home to for nearly 1,000 years. According to the , it is the oldest and largest occupied castle in the world, and it's still a working today. Built shortly after the Norman conquest, construction began around 1070 under William the Conqueror. Just 16 years later, the fortress was completed. Over time, it became a royal palace and is now one of the most famous castles in the world.

Experts at say it contains over 1,000 rooms, including state apartments, a chapel, a royal library, and more than 300 fireplaces.

It's currently home to over 500 residents and staff, from chefs and gardeners to butlers and librarians.

At least 40 monarchs have lived there, and many big royal events have taken place at the castle, including Prince Harry and Meghan Markle's wedding at St George's Chapel.

As far as earlier history is concerned, in the 14th century, Edward III transformed Windsor into a huge Gothic palace.

Later, in the 1800s, George IV made extensive changes, including raising the Round Tower and creating the Grand Staircase.

The Royal Collection Trust says his renovations alone cost nearly £300,000, which was a huge sum at the time.

The castle suffered a major fire in 1992, which damaged several rooms, including St George's Hall and the Grand Reception Room.

Restoration took five years and was completed in 1997. Work continued in later years, and in 2020, the Inner Hall was reopened as part of a new visitor route.

Today, Windsor Castle welcomes around 1.5 million visitors each year.

According to the , entry to the castle costs £31 for adults, £20 for young people aged 18-24, and £15.50 for children when booked in advance.

Tickets include access to the State Apartments, St George's Chapel, and The Semi-State Rooms when open.

Windsor Castle is open to visitors throughout the year.