Discover the Amazing Carvão Caves in São Miguel, Azores

Exploring the Carvão Caves

On our recent visit to São Miguel Island in the Azores, we visited one of the archipelago’s most interesting natural geological phenomena, the amazing Carvão Caves near the city of Ponta Delgada.

The caves were first discovered in the 16th century and have been a source of wonder for locals, visitors and researchers ever since.  Below is a detailed account of what you can expect when visiting the Carvão Caves in São Miguel based on our personal experience taking the tour.

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Highlights of the Carvão Caves of São Miguel Island

What Are The Carvão Caves in São Miguel, Azores?

The Carvão Caves on the island of São Miguel are the result of a volcanic eruption that occurred approximately 10,000 years ago.  The caves were formed by the flowing lava which, as it cooled, formed a crust, while lava below the crust continued to flow leaving a hollow “lava tube”.

Since the Azores themselves were formed by a series of volcanic eruptions, there are many such caves throughout the islands. In fact, there are 271 throughout the archipelago and 28 are known to exist on São Miguel.

Carvão Caves is the largest, originally thought to reach more than 5 kms, in São Miguel and is considered to be one of the most remarkable in the Azores.  It was declared a Regional Natural Monument by the government in 2005.

Visiting the Caves

Getting to the caves, known locally as Gruta do Carvão, is relatively easy if you are staying in Ponta Delgada.  The caves are located a short 10-minute drive north of the downtown area and just off the Secunda Circular highway.  

Carvão Caves In San Miguel Tickets

The only way to see the caves is via a guided tour purchased at the ticket office. Reservations can be made by calling or emailing and are recommended as the tours are offered at specific times and they fill up fast.

There are two types of tours offered: a short tour that lasts 35 – 45 minutes and goes out at 10:30, 11:30, 14:30, 15;30 and 16:30 daily.  This covers about 200 metres of the caves and is considered an easy walk, although it is not accessible for those with reduced mobility as there are a couple of flights of stairs and the cave floors are quite uneven.  

This tour has a cost of 9 euros per person and is available for anyone over the age of 7.

The longer tour lasts about 2 hours and is by appointment only.  This tour has a difficulty level of medium and covers about 1000 metres of the cave.   It is ideal for those that are really interested in speleology (the study of caves) and has a cost of 25 euros per person.

Inside The Carvão Caves

We chose the short tour and we found it to be quite informative.  Our guide was a geologist who had extensive experience and a lot of passion for the very special geological structures of the cave system.

Even though it was fairly mild outside, we were encouraged to bring a light jacket as the temperatures in the cave were quite cool.  From the main floor of the ticket office, we descended a couple of flights of stairs to a landing area where we were given hard hats fitted with a light and given some general safety instructions.

After donning our hard hats we were led through the cave entrance to a large cavern where we got our first view of the various types of solidified lava and volcanic rock.

Descending Underground

It was quite surprising how large the cavern was in this location.  It was also interesting to see the different colours of rock embedded in the walls of the cave.

To give us an idea of how dark it is inside the caves, our guide turned off the spotlights that highlight the sides of the cave and asked us to switch off the lights on our helmets temporarily.  The total blackness that surrounded us was eerie and we were glad when we turned our lights back on.

Explaining The Geology

The guide explained that there are different densities of rock that formed the cavern as a result of the different temperatures of the lava flow during the eruption.

Some of the rock was quite heavy and dense and we were surprised at how much it weighed when he passed around a sample he had picked up from the cave floor. 

The heavy rock was caused by the lava when it reached a temperature of 1200 degrees Celsius.  This high heat caused the gases to evaporate quickly, so there were no bubbles in the lava, making it quite dense and heavy.

Rocks formed from the lava when it was a much cooler, 600 degrees Celsius, and had more gas in the lava resulting in a softer, lighter rock. While observing the lava you can also see various colours that indicate the iron oxide that is prevalent within the rock formations.

One of the interesting phenomena of the Gruta do Carvão is that, unlike most other caves, the stalactite and stalagmite are very short. This is due to the lack of minerals in the water that filter through the cave.  The water is so soft that there is little in the water for the formation of deposits that create the stalactites.

The Fascinating Science

Our guide shared with us that one of the recent discoveries in the caves was of a special type of rare bacteria.  Scientists have been able to determine that this bacteria can be used as an antibiotic for the treatment of human infections.  

In fact, there are more than 800 species of endemic bacteria in the caves and a lot more research is being carried out to determine what other benefits there might be.

Interesting Facts About the Carvão Caves

✦ Before Gruta do Carvão was declared a Regional Natural Monument residents used it as a garbage dump and 22 tons of garbage needed to be removed before it was open to tourists.

✦ At one time, the caves were used to store food.  The cool temperature in the caves acts as a natural refrigerator and makes the perfect location to keep food from spoiling.

✦ The discovery of the caves presented quite a challenge to urban planners because parts of Gruta do Carvão pass directly under buildings, water treatment plants, sewers and highways. The short tour has a section that goes directly under the main highway passing north of Ponta Delgado.

The Final Word…The Amazing Carvão Caves in São Miguel, Azores

If you are looking for a truly unique site that offers a rare glimpse into the special geological structure of the volcanic island of São Miguel then you should definitely visit the Gruta do Carvão in Ponta Delgado.  

This natural geological museum is easy to get to, relatively inexpensive and the perfect place to visit, even in the rain!