Four Hand-Dug Underground Places You Can Walk Into

The deepest place on this list goes down about 280 feet (85 meters). The shallowest kept a citrus tree with eight grafts about 22 feet below the surface in Fresno. All four were cut by hand into rock soft enough to dig, and all four let visitors walk in. They run here from deepest to shallowest.

1. Derinkuyu Underground City

Nobody agrees on how many floors Derinkuyu Underground City has. The Turkish Museums portal, run under the Ministry of Culture and Tourism, counts eight. Other accounts give five, and some give 18. The depth is less disputed: roughly 85 meters, cut into volcanic tuff that carves easily and hardens once it meets the air. Estimates put its capacity at up to 20,000 people, along with their livestock and food.

The builders left no name. The ministry's own entry calls it a hiding place from the period when Christianity was spreading and estimates it was built in the 9th and 10th centuries. Other accounts push the first chambers back to the Phrygians, around the 8th century BC, with Byzantine Christians expanding the complex as a refuge during the Arab-Byzantine wars. Each level could be sealed with a rolling stone door that opened only from the inside. The wells could be closed off against poisoning, and the ventilation shafts still work.

Greek speakers in the region called the place Malakopia, a name probably taken from the Greek word for soft. Local people still used it in the 20th century. In 1923, the region's Christian population was sent to Greece in the population exchange between Greece and Turkey, and the city was abandoned. In 1963, a resident renovating his house knocked through a basement wall and found a room behind it, and further digging exposed the tunnel network.

About 10 percent of the network is open to visitors. Tickets are sold at the gate or online, hours change with the season, and a guide is optional.

2. The Longyou Caves

For about 2,000 years, the caverns at The Longyou Caves sat full of water, and the water may be why they are still standing. In 1992, four farmers in Shiyan Beicun pooled money for pumps and emptied ponds the village had always taken to be bottomless. Under the water were carved chambers. Li Lihui, a geologist at the Chinese Academy of Sciences' Institute of Geology and Geophysics, has argued that weakly acidic water sitting against weakly alkaline siltstone kept the rock stable and slowed its weathering. The five caverns that were pumped dry have since cracked, seeped, and dropped small rock falls, and Li's 2022 abstract calls an entire roof collapse "highly possible in the near future" in each of them.

Most accounts give 24 caverns, while a China Daily tourism page and Showcaves.com give 36. Showcaves.com puts the chambers about 100 feet (30 meters) underground. Every surface carries the same tooling, bands about 2 feet wide filled with parallel chisel lines set at a steady angle, across walls and ceilings alike. The rest of the inventory is thin: a headless statue and carved figures of a horse, a fish, and a bird. No inscription, burial, or household debris has been found, and no historical document records the work.

Accounts differ on how many caverns a ticket covers. Showcaves.com says one is open; other travel listings describe the five pumped-out caverns. Inside, the open space is lit, floored, and cool year round, with stairs and railings. The stairs rule out wheelchairs. The colored lighting flattens the tool marks, and looking along a wall rather than straight at it brings them back. Longyou sits between Hangzhou and Quzhou, with fast trains to both, and the site is a short taxi ride from town. A visit takes an hour or two.

3. Ħal Saflieni Hypogeum

When Themistocles Zammit excavated the Ħal Saflieni Hypogeum in the early 1900s, he estimated, by his own account very roughly, that it held the bones of at least 6,000 to 7,000 people, mixed with animal bones. The complex was in use from about 4000 BC to 1500 BC, dug in three levels into globigerina limestone, with its users digging deeper as space ran out. The deepest room lies about 35 feet (10.6 meters) below today's road. One chamber on the upper level still holds its original burial deposits.

The most repeated thing about the site is the sound in a small room decorated with spirals, called the Oracle Chamber. A 1920 account by Griffiths says a word spoken there is "magnified a hundredfold and is audible throughout the entire structure."

In 2017, the acoustician Rupert Till published the first systematic measurements in the journal Antiquity (author copy). With a source in the Oracle Chamber and a microphone outside it, low tones at 63Hz kept sounding for more than 13 seconds. Speech carried everywhere and could be understood almost nowhere: Till rated intelligibility "worthless" anywhere but right beside the speaker. Earlier writers, and a 2014 study, said a deep male voice is what sets the room ringing. Till's numbers did not bear that out: male and female speech came out equally clear, and the long ringing traced to low frequencies from any source.

A stonemason found the site in 1902 while laying foundations for houses in Paola. By the time anyone reported it, most of the houses were finished, and the upper level had been damaged beyond repair. The state took it over by the end of 1903.

The visiting rules are the strictest on this list. As of October 7, 2026, Heritage Malta's Hypogeum page says only 10 people are allowed inside at a time, because carbon dioxide, temperature, and humidity all rise with every body in the rooms. Regular tickets are sold online and at any Heritage Malta site, and Heritage Malta strongly recommends booking early; Malta's tourism authority says tours are often full weeks in advance. Last-minute tickets go on sale only the day before a visit, first come, first served: at Fort St Elmo and the Gozo Museum of Archaeology until 12pm, then also at the National Museum of Archaeology, the Domvs Romana, and the Hypogeum itself. One buyer can take up to 4, with an exception for families. Photography is not allowed, children under 6 are not admitted, and audio guides run in seven languages. The statuette known as the Sleeping Lady, found here, is on show at the National Museum of Archaeology in Valletta.

4. Forestiere Underground Gardens

On March 23, 1923, the Fresno Bee ran a story headlined "Resort Underground" about a vineyardist digging rooms under his ranch, and reported that "no plans were made." Baldassare Forestiere, from Filari in the Sicilian province of Messina, dug into the hardpan under his land from about 1906 until 1946 with a pick, a shovel, and a wheelbarrow, in the time left over from his farm work. The Forestiere Underground Gardens began, by the 1977 National Register nomination's account, as a "retreat to escape the excessive heat."

Counts of the rooms vary. The Bee found 50 in 1923 and 1924. Later sources give 65 rooms on three levels, or more than 100 rooms and tunnels. The nomination describes courts and grottos joined by passageways, an automobile tunnel some 800 feet long, and ceilings carved "like inverted tea cups." Citrus, figs, olives, dates, jujube, and carob grew in hardpan planters under skylights. One tree, about 22 feet below the surface, carried eight grafts of citrus, and in 1977 seven of them were still bearing fruit. The family's site says he "never officially opened the Mediterranean resort of his dreams." A roadside architecture website tells of a childhood sweetheart in Sicily who refused to join him. That website gives no source, and neither the nomination nor the family's history mentions it.

The official FAQ gives the main touring season as March through November. As of October 7, 2026, the operator's booking calendar listed October tours Thursday through Monday and November tours Friday through Monday plus Wednesday, November 25, with departures from 9am to a last tour at 3pm and nothing listed after November 30. Tours last about an hour, with about 20 stairs, all with handrails. The operator's accessibility page gives groups of up to 18, and its tour page gives 16. The rooms run 10 to 15 degrees cooler than ground level. Tours close for rain and extreme heat. Personal photos are allowed; video and panoramic photos are not. The fruit on the trees is not for picking. High-speed rail construction has changed traffic and parking around the site, and the operator asks visitors to arrive 20 minutes early.

Craig Kohlruss of the Fresno Bee filmed the excavation for this 2-minute video from 2024.

Three of these four places have no digger's name attached. The fourth has one man, who wanted to be buried in his gardens and lies instead in Holy Cross Cemetery, about 5 miles south.