Algar Do Carvão: The Volcano Chimney You Walk Into

What the Algar is

Algar do Carvão is a volcanic chimney, not a lava tube. When the last eruption inside the island ended, the vent above it stayed open, and today you can walk straight into that empty volcanic shaft through the crater mouth at the top, which measures 15 x 20 m. The chimney drops 90 m to a lake of rainwater at the bottom.

Very few volcanoes on earth leave a vent you can enter on foot, which is why the site is an Azores Geopark geosite and was a finalist in the 7 Maravilhas Naturais de Portugal competition. The cave itself is dated about 2,148 years old, give or take 115 years. On terceira, the island pairs it with the Gruta do Natal lava tube in the same interior.

The 1973 donation

Ownership is the detail most blogs get wrong. The site was donated to Associação Os Montanheiros in 1973 by José Ataíde da Câmara and his wife, and the association still runs it today. It is not managed by the regional government's natural parks network and not by Amigos do Açores.

That matters practically: the operator's own page on montanheiros.com is the only reliable source for the Algar's hours and prices, and it differs from the government-run park infrastructure on the same island. This guide treats montanheiros.com as the source and copies its season bands and its €10 entry price exactly as published.

The descent, 338 steps down

You walk in through the crater mouth and down a stairway of 338 steps into the vent. The walls open out as you go and the daylight shrinks behind you, which is a strange feeling because the crater mouth stays visible overhead as a hole of daylight. The operator's published visit duration is about 30 minutes, and that counts the full down-and-back.

The steps are the return route too, so the climb back up is real and worth pacing. Take your time on the way down and you will have an easier trip out.

The lake at 90 m

The chimney ends 90 m below at a lake fed by rainwater. The water can reach a maximum depth of 15 m and a surface of up to 400 m². Because the water comes from rain, the level moves with the seasons, so the shoreline you see at the bottom depends on when you visit.

In a wetter stretch the lake sits higher up the walls, in a drier one it pulls back and exposes more rock. Either way it is the turning point of the visit, the floor of the vent where the stairs end.

Milky-white silica stalactites

Water depositing through the rock has built stalactites and stalagmites of amorphous silica in a milky white, and the walls carry reddish veins of limonite, an iron ore. This mineral pair is the cave's signature and few caves show anything like it. The white formations hang in the upper parts of the vent where the light from the crater mouth still reaches, which is why they photograph best from the footbridge.

Bring a camera that handles low light if you want the detail.

The plant-covered crater mouth

The opening at the top, 15 x 20 m, is green with vegetation hanging down into the vent, ferns and mosses thriving on the light and moisture that pour through the hole. That green frame is what every photograph of the Algar uses, and you see it from below as you climb back up. The floor of the crater bowl above is the first stop before the steps, and it is worth a look from the rim too, since it shows you exactly how narrow the shaft you are about to enter really is.

The cave closes seven dates a year: 1 January, Easter Sunday, 1 December, 25 December, plus Carnival Tuesday, 24 December and 31 December. There is no winter season as such, the cave simply runs fewer days, four afternoons a week from October to December and in the last stretch of March, daily from April through September.

Crowds follow the clock. The stairway is single-file in places, so when a summer session opens at 14h00 the first visitors bunch up on the steps and the queue moves slowly for the first stretch of the afternoon. Arriving mid-session usually means more space on the stairs. A rainy stretch of weather can also move the lake level at the bottom, which changes the look of the chamber. Plan the cave for the afternoon and route the island's mornings around it.

Opening hours by season

The season bands below are copied from the operator Os Montanheiros' own page, montanheiros.com, and they decide everything about when a visit can happen.

The Algar was temporarily closed for construction of a new visitor centre, the Centro Açoriano de Vulcano-Espeleologia, CAVE for short. Visits resumed in March during the final construction phase. That means the cave is open, but the works continue around it, and the operator warns that visits can be suspended at short notice while the build finishes.

The practical advice is simple: check montanheiros.com on the day you plan to drive, especially in the shoulder months when the cave only opens four afternoons a week and a suspension wipes out half the week's sessions. The construction touches a visit in a second way too. The combined ticket that once covered the Algar and Gruta do Natal at a reduced price is suspended during the works, so for now each cave charges its own entry. No date for a return to full normality has been published, so treat any reopening timeline you read elsewhere as a guess.

The cave sits about 12 km from the city of Angra do Heroísmo in the island's interior, at roughly 640 m altitude, at GPS 38°43'41.54"N 27°12'59.01"W. Access is by car. No public transport is published to the cave, and that is the single most useful practical fact on this page, because it is the reason the cave tours sell. If you are driving, our page on getting around azores covers the island logic and azores car rental the hire side.

By air, Azores Airlines sells tickets from Boston, Toronto and Montreal direct to the island's TER airport, so North American visitors can land on Terceira itself rather than connecting through the archipelago's capital. By sea, the island's Atlânticoline ports are Angra do Heroísmo and Praia da Vitória, but the ferry timetable is a dynamic search tool and no static per-route fares are published, so plan crossing times through the operator's booking tool. Note there is no Ponta Delgada ferry port in the network, so you cannot sail directly from São Miguel. A rental car for the afternoon is the standard plan, paired with Furnas do Enxofre or the Gruta do Natal in the same interior.

Time planning table

The table plans a day around the visit, using the operator's own 30-minute figure for the cave and the platform's own prices for the tours, with the rest labelled our estimate.

- It is not a lava tube, it is a volcanic chimney, a vent left open above the eruption, and its crater mouth measures 15 x 20 m (montanheiros.com). - The cave is dated about 2,148 years old, give or take 115, and it is an Azores Geopark geosite that was a finalist in the 7 Maravilhas Naturais de Portugal (montanheiros.com). - The stalactites are milky-white amorphous silica and the wall veins reddish limonite, an iron ore, a mineral pair few caves show (montanheiros.com). - The site belongs to a volunteering association, donated in 1973, which is why its ticketing and hours differ from the government-run parks on the same island (montanheiros.com). - No public transport reaches it, so every figure for a bus trip you see online is invented, the working car-free option is a tour with transport (montanheiros.com, no public transport published).