This Santorini sister island is Greece's best-kept secret

A hunk of black volcanic rock rearing out of the Aegean Sea, Therasia is by no means invisible. The Greek island was forged in the volcanic blast that created Santorini some 3,600 years ago, shares the same caldera waters and postcode, and serves as a photographic backdrop for the 3.4 million travellers who visit its better-known neighbour each year. Yet, few can name the isle of 168 inhabitants, and even fewer visit.

Despite it being just a 10-minute, £1 ferry ride from Santorini’s Ammoudi Port — right next to the famous whitewashed houses of the village of Oia — reaching Therasia was long seen as something of a hit-and-miss affair due to the lack of printed timetable. However, there have been various changes across the sleepy outpost in the wake of the pandemic. Last year, the single road gained an automated petrol pump (previously, petrol was dispensed only by appointment). The ferry schedule can now be found online. And a growing number of tourism-related offerings have popped up.

Opened in 2024 by couple Paris Savvidis and Dimitris Kriezis on Paris’s ancestral land, and run with true philotimo (hospitality), Santa Irini Retreat by the main Riva port offers the type of whitewashed boutique stay characteristic of the Cyclades. A traditional building has been separated into four house-like suites, with handwoven antique fabric headboards, decorations made of driftwood sourced from the nearby beach, and iron, hourglass-shaped room keys. It’s the sort of destination that invites guests to slow down and take in their surroundings, whether that’s strolling around the fig trees in the garden or enjoying the sunset views from a poolside sunbed. 

Also on the grounds is Santa Irini, the family church. Its tiny size belies its significance as Santorini’s namesake: when homecoming sailors sighted the 1867 whitewashed building at the neck of the caldera, they’d celebrate another safe return, shouting “Santa Irini!”. There are 23 other churches across Therasia — something of a feat for a destination that’s just 5.5 miles long and 1.5 miles wide. At its other end is the Monastery of Kimisis, whose cobalt blue dome — almost identical to the ones found in Oia across the inky caldera — teeters on the rim of Trypiti Cape volcano. 

The smaller port at Korfos Bay caters to caldera boat tours. Beaches aren’t Therasia’s strength — there are black-pebble stretches by Korfos Cove, Riva Port and Santa Irini — and day visitors rarely venture beyond Korfos’s restaurants. It’s worth climbing the 280 steep stone steps to the main village of Manolas, built at the island’s apex to guard against the likes of Ottoman corsair (pirate) Barbarossa, who terrorised these parts in the 1500s. Walk its snaggle of whitewashed lanes to peek into cave houses and enjoy vertiginous views of Korfos Cove and Santorini.

The village is also home to Fyrgano restaurant, a local favourite featuring farm-to-fork Greek salads made with produce from the owner’s garden. Continue past the downstairs kitchen and seating to an upstairs terrace. Further down the pedestrianised street is Panorama Resto, offering higher-end, creative dishes like baby calamari moussaka and fresh sea bass fillet in beetroot hummus and Tinos sea fennel.  

For something to drink, Mikra Thira winery near the hamlet of Potamos is housed in an ultra-modern building that could easily be mistaken for something from the Napa Valley. Therasia’s volcanic terroir shares similarities with Santorini's, and its vines are also grown in the traditional koulouri — ground level, wreath-like baskets that protect them from the Meltemi winds (seasonal northerly winds that blow mainly over the Aegean during summer). The 90-minute vineyard and production tour includes tastings of three assyrtiko (Greek grape) varieties at the sophisticated cellar door.

The winery can also be pin-dropped as a stop on a tour with Explore Thirasia, founded by avid biker Yannis Daskalakis and offering hiking, mountain bike and e-bike excursions. The island’s lack of cars, small size and easily won views make it perfect fort cycling. The company’s morning or sunset walks offer ideal opportunities to wind through the brush, the scent of wild thyme heavy in the air. A highlight is the abandoned cave house settlement of Agrilia, set in a gorge. Only a few decades ago, it housed an agricultural community of up to 700 people, but its fortunes changed as the tomato paste factories it supplied closed after the Second World War, and then a 7.7-magnitude earthquake struck in 1956.

On a narrow hiking path past windmills and relics from the Minoan, Venetian and Ottoman occupation, you’ll also stumble into what locals refer to as ‘The Mexican Church’. Officially called the Church of the Virgin Mary, its peach and yellow hues are as much a surprise as the nearby disused mines that once provided pumice stone for building the Suez Canal. 

This little island rewards visitors who are prepared to put in a little more effort, go that extra mile and come with an open mind.