Check out this optical illusion made from chalk

People have been posing with the artwork which makes them look like they're sitting on top of castle walls

You might be using chalk to draw in your garden this summer, but could you create an optical illusion like this one?

The street art celebrates the reopening of a water gate at Caerphilly Castle and was drawn outside Cardiff Central railway station.

It was created by Julian Beever, a chalk artist known all around the world.

He said: "It's been brilliant to see so many people stop, stare, and realise they're literally standing on history."

The artwork will eventually move into castle grounds alongside new interactive exhibits.

The artwork shows the medieval entrance to the great hall at Caerphilly Castle, which has been hidden from view for centuries.

It celebrates the first time the water gate has been opened since medieval times.

The passageway connects the castle's great hall to the southern lake and was originally used as a way to get into the castle from the water's edge.

It's part of a big regeneration project costing £8m, which wanted to "breathe new life" into one of Wales' most iconic landmarks.

Gilbert de Clare started the construction of Caerphilly Castle in 1268, and it's still the biggest castle in Wales.

It's three times bigger than the home of Welsh rugby - the Principality Stadium.

As you can imagine, a building this old needs lots of work to keep it in good condition, which is why it needed a restoration project.

The water gate is just one of several improvements made to the castle alongside the refurbishment of the great hall.

Gwilym Hughes, head of Cadw who is responsible for looking after Wales' historical places, said:

"Breathing new life into Wales' heritage isn't just about restoring old walls, it's about opening doors to stories old and new, welcoming visitors from near and far, and captivating future generations."