Map Tunnel — Where Would You Come Out?

By Marko Visic · Updated Oct 7, 2026

If you dug a perfectly straight tunnel through the Earth, where would you emerge? Two globes side by side, synchronized in real time. Pan or rotate the left one and the right one rotates to your antipode — the exact opposite point on the planet. Search a city, tap Use my location, or click anywhere on the left globe to start the tunnel.

The Map Tunnel is a dual-globe antipode visualiser. The left globe is the entry — where the tunnel begins — and the right globe is the exit, the point on Earth's surface diametrically opposite the entry. Both views are real OpenStreetMap data rendered as 3D globes, and they stay mathematically locked: drag one and the other rotates in mirror in real time, so you can sweep across a continent and watch the opposite side of the planet trace out as you go. Below the maps the tool reads back the country or ocean at each end, your hemisphere, the chord through Earth's core (a constant 12,742 km), the great-circle distance over the surface (a constant 20,015 km), and the 12-hour solar-time flip between the two ends. Most tunnels — about 95% of them — emerge in open ocean. The fun is finding the rare pairs that don't.

What is a tunnel through Earth, really?

A "tunnel through the Earth" is shorthand for the line that connects any point on the surface to its antipode — the point on the opposite side of the planet, passing through the center. For any point at latitude φ and longitude λ, the antipode is at (-φ, λ ± 180°). Latitude flips sign (north becomes south); longitude shifts by exactly half the world (east becomes west or vice versa).

The tunnel itself, if it could be drilled, would be exactly 12,742 km long — the mean diameter of the Earth. Along the surface, antipodes are 20,004 km apart pole to pole and 20,037.5 km apart along the Equator on the WGS-84 ellipsoid. On a sphere with Earth’s mean radius (6,371 km) the distance is 20,015 km (π × 6,371). These numbers are constants: they do not change with where you start.

What does change is what you find at the other end. The Earth is about 71% ocean, so most tunnels emerge in open water. About 13% of the world’s land has land directly opposite it, which is about 4% of Earth’s surface (our calculation from Natural Earth 1:50m land polygons, October 2026). The Map Tunnel makes that visible: drag the left globe across the United States and the right globe sweeps across blank ocean; drag it across central China and the right globe traces a clean line across Argentina.

How to use the Map Tunnel

Five simple paths — pick whichever fits your context.

1. Pick your starting point. Type a city, address, or landmark in the search box; tap the GPS button to use your current location; or click anywhere on the left globe. The left pane is the entry — where you start digging.
2. Watch the right globe rotate to your antipode. The right globe — the exit — instantly rotates to the antipode (the point exactly opposite on Earth). The two globes stay synchronized: drag one and the other follows in mirror, so you can rotate the planet and watch the tunnel emerge anywhere.
3. Read the through-Earth and around-Earth distances. Below the maps the panel shows the chord through Earth (a constant 12,742 km / 7,918 mi — the diameter), the great-circle distance over the surface (20,015 km / 12,437 mi — half the great-circle circumference), and the time-of-day flip on the opposite side.
4. Click the right globe to invert the tunnel. Clicking the antipode globe sets the entry to the antipode of where you clicked — the inverse direction. Useful for asking "if someone dug through to me, where would they have started?"
5. Swap, reset, or copy the coordinates. Use Swap to mirror entry and exit. Use Reset to clear and start over. The entry and exit coordinates are shown in standard decimal-degrees format below each globe.

What people use the Map Tunnel for

Six common use cases.

Famous tunnel pairs — what is on the opposite side?

A reference of well-known cities and what lies on the other side of the planet. Most tunnels emerge in ocean, which is why the few land-to-land pairs are famous.

The numbers behind the tunnel

Every value displayed in the result panel comes from a small set of Earth-shape and Earth-interior constants. The numbers below are the basis of every figure in the tool.

The physics of a hypothetical tunnel

1. Could it actually be drilled?

No, not with anything resembling current technology, and probably not ever. The tunnel would pass through the Earth’s mantle (1,000–2,500 °C), the outer core (liquid iron at 4,000–5,400 °C), and the inner core (5,200 °C, solid iron under 360 GPa pressure — about 3.6 million atmospheres). The deepest borehole ever drilled — the Kola Superdeep Borehole — reached 12,262 meters, which is 0.19% of the way to the center. The borehole was abandoned because at 180 °C the rock behaved more like plastic than rock and the drill bit kept getting stuck.

2. The gravity-tunnel problem

In the classical physics problem (frictionless, airless, uniform Earth), an object dropped into a straight tunnel between antipodes oscillates back and forth like a pendulum. The half-period — the time to "fall" from one side to the other — is approximately 42 minutes 12 seconds, regardless of which two antipodes you connect. At the center the object would be moving at about 7.9 km/s — roughly the orbital velocity at the Earth’s surface — and the gravity would be zero (all directions of mass cancel).

3. Why all tunnels take the same time

It is a beautiful result of simple harmonic motion: in a uniform-density Earth, the time to fall through any straight chord — not just the diameter — is the same. A tunnel from New York to Beijing (chord of about 11,000 km) takes the same 42 minutes as a tunnel from New York to its true antipode in Western Australia. This is the basis of theoretical "gravity train" proposals from the 19th century onwards.

4. The Coriolis problem

A real Earth-tunnel object would not fall straight down because the Earth is rotating. At the equator the surface moves east at about 1,670 km/h, while at depth the rotational speed is lower. An object dropped into a vertical tunnel would press against the eastern wall on the way down — a mile of horizontal drift over a 6,371-km depth. This is why gravity-tunnel proposals always assume a thought-experiment Earth: non-rotating, uniform, airless.

Why most tunnels emerge in ocean — the 71% rule

Earth’s surface is roughly 71% ocean. If land were uniformly distributed, the probability that a random point and its antipode are both on land would be about 8.4% (29% × 29%). Empirically the figure is even lower — about 4–5% — because landmasses are correlated: most land is concentrated in the northern hemisphere, with large oceans (Pacific, southern Indian, southern Atlantic) on the opposite side.

The major land-to-land tunnel corridors are:

1. East Asia ↔ South America. China ↔ Argentina covers about 2.0 million km², plus China ↔ Chile (0.45 million) and Mongolia ↔ Argentina (0.27 million). It is eastern and central China that sits opposite Argentina and Chile; western China and Tibet are opposite the Pacific.
2. Greenland ↔ Antarctica. About 1.8 million km².
3. Arctic Canada ↔ Antarctica (1.5 million km²) and Arctic Russia ↔ Antarctica (0.6 million km²).
4. Southeast Asia ↔ northern South America. Indonesia ↔ Brazil (0.5 million km²), Indonesia ↔ Colombia (0.32 million) and the Philippines ↔ Brazil (0.25 million), plus smaller pairs with Venezuela, Malaysia and Vietnam–Peru.
5. Spain ↔ New Zealand. Smaller. Portugal’s antipodes fall just off New Zealand’s west coast, in the Tasman Sea.
6. Hawaii ↔ Botswana. Small.

Map Tunnel vs Antipode Finder — when to use which

Both tools answer the same underlying question. The choice depends on what you want to see.

• Map Tunnel (this tool) — two side-by-side globes, synchronized. Best for visual comparison, lessons, and content where the "two real places at the same scale" framing matters. Drag-sync makes it easy to sweep a region and watch the opposite side trace out in real time.
• Antipode Finder — single map with both pins. Best for one-shot lookup, sharing a screenshot of a specific antipode pair, or copying coordinates in DD / DMS / DDM with country and ocean metadata.

The word "antipode" — etymology and history

"Antipode" comes from the Greek antípodes — literally "feet opposite", from antí (opposite, against) and poús (foot). In ancient Greek geography, the antipodes were thought to be a hypothetical race of people living on the other side of the spherical Earth, "with their feet against ours". The word entered English in the 14th century with the same meaning.

Capitalized, "the Antipodes" is a colloquial British term for Australia and New Zealand — because they are roughly antipodal to the British Isles. Geographically the term is loose: London’s actual antipode is in the South Pacific, not in New Zealand. But the historical association is firm enough that "Antipodes" remains a common shorthand for the region.

Related tools and resources

For a single-map antipode lookup with country and ocean metadata: Antipode Finder. For the great-circle distance between any two specific points (not just antipodes): Distance Between Two Places. For the geographic midpoint between two locations (the opposite of an antipode pair): Halfway Between Two Places. For converting the antipode coordinates into DMS, DDM, UTM, or Plus Codes: GPS Coordinate Converter. To find the latitude and longitude of any place: Latitude & Longitude Finder. To see the day-night terminator and where it currently is on Earth: Day Night Map.

Frequently asked questions

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