The Blue Grotto is a set of sea caves under the cliffs at Wied iż-Żurrieq, on the south coast. Small boats run out to them from the inlet.
The blue everyone photographs is sunlight passing through the water and reflecting off the pale sea floor into the cave.
It needs the sun at a low angle from the east. It happens in the morning and stops by early afternoon.
When to go
Between about nine and eleven is the window.
Earlier than nine the sun is too low to reach in. After midday the light comes from overhead and the water turns ordinary.
Go in the first half of the morning and you also miss the coaches, which arrive from about eleven.
Summer is better than winter for it, because the sun sits higher and reaches further into the caves.
The boats
Trips leave from the quay at the bottom of the valley. They take about 25 minutes and cover several caves, not only the main arch.
Tickets are bought at the kiosk on the quay rather than online. Expect around €10 a head and cash is safest.
The boats are small and open, and they seat eight or ten. There are no seatbelts and no roof.
They do not run when there is any swell from the south or southwest, and the decision is made that morning.
If the boats are cancelled
The viewpoint on the road above the inlet is free and open in any weather.
It gives you the arch from above and is where most of the photographs are taken from.
There is a small parking area there and a cafe across the road.
Park in the village and walk down rather than driving to the quay, which is narrow and fills early.
While you are there
Ħaġar Qim and Mnajdra are ten minutes away by road and share one ticket.
There is swimming from the rocks at the inlet, and it is deep straight off the ladder.
The Um El Faroud wreck lies offshore from the same inlet, which is why the quay is full of dive kit most mornings.
The village of Żurrieq is up the hill, with a proper square and bars that are not aimed at visitors.
Practical notes
There is no shade at the quay and the walk back up the valley is steep.
Buses run from Valletta and from Żurrieq. The stop is at the top, not at the water.
Allow an hour and a half for the whole thing, including the walk and the wait for a boat.
