Ganh Da Dia

Ganh Da Dia is a bed of columnar basalt on the Phu Yen coast where a lava flow cooled and contracted into vertical prisms, mostly five and six sided, packed together and truncated at the same level so that the surface reads as a floor of stacked plates - the name means the reef of stone plates. The columns run out into the sea and are washed over at high water. It is the most complete formation of its kind in Vietnam and is usually compared to the Giant's Causeway, which is the same process on a different flow. A national monument, with a path and steps down from the clifftop.

What you actually see

• Five and six sided basalt columns - packed and truncated at one level.
• A surface like stacked plates - which is where the name comes from.
• Columns running into the sea - washed over at high water.
• The most complete such formation in Vietnam - and a national monument.

When to go

February to August, avoiding the wet season storms. Half a day.

Honest expectations

The rock is slippery when wet and waves come over the lower columns. It gets busy with Vietnamese visitors at weekends and holidays. Facilities are a car park, steps and a few stalls. There is no shade.

Nearby

O Loan lagoon is south; Tuy Hoa and the coast run down towards it.