Blue Cave of Xiji Islet
A sea arch in southern Penghu where light through the water turns the inside of the cave an intense blue.
Updated 2 September 2026
Xiji is an uninhabited basalt islet in the far south of Penghu, and on its side is a sea arch that small boats can enter when the water is calm. Light coming through the water and reflecting off the pale bottom fills the chamber with blue, the same effect as the better-known caves in the Mediterranean. Boats hold inside for a few minutes and back out. Whether the trip runs depends entirely on the swell.
What's there
- The blue light - sunlight through the water filling the chamber with colour.
- The sea arch - the basalt opening boats pass through into the cave.
- The islet cliffs - columnar basalt around the uninhabited island.
- The southern sea - clear water around the outer Penghu islands.
When to go
May to September is the season and calm mornings are when boats can enter. Any swell cancels the cave section of the trip. Winter is out of the question.
What to expect
Entry depends on the sea state and is cancelled often, even on trips that run. The stop lasts a few minutes. The blue is strongest around the middle of the day and weak in cloud.
Nearby
Dongji and Xiji are the outer southern islands, and Magong is north.
What to pack for Blue Cave of Xiji Islet
Chosen from what this place is for. Tap a kit for the full checklist.
- Broken-in walking shoes or boots - Grip and ankle support matter more than looks; never hike in brand-new boots. Find on Amazon
- Head torch + spare batteries - Hands-free light is essential; caves are truly dark. Find on Amazon
- Layers + a waterproof shell - Mountain weather turns fast; a packable rain jacket saves the day. Find on Amazon
- Grippy closed shoes - Cave floors are wet, muddy and slick with formations. Find on Amazon
Some links on this page are Amazon affiliate links - if you buy through them we may earn a small commission at no extra cost to you.
All packing kitsPlan your trip
Where to start if Blue Cave of Xiji Islet is going on the list.
Booking links on this page are affiliate links - if you book through them we may earn a small commission at no extra cost to you. It never changes what we write about a place.
Opening times, ticket prices and seasonal closures change - check the official source before you go: official site.
