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Top 10 Famous Astronomical Observatories

By Dhiraj Sharma · Published October 30, 2026 · Updated November 2, 2026

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Infographic of famous astronomical observatories, showing white telescope domes on a mountain under the Milky Way, with callouts for Greenwich, Jantar Mantar, Mount Wilson, ALMA and Rubin Observatory

Famous astronomical observatories range from Greenwich, home of the prime meridian, and Jaipur's giant stone sundial to Chile's desert telescopes.

This Finepedia guide, written in October 2026, visits ten observatories that changed how we see the sky, from royal buildings of the 17th century to a survey telescope that began its main work in 2026. Each entry explains where the observatory stands, what its instruments do and one discovery or story linked to it. For more on space, see the Finepedia guides Top 25 Interesting Facts About the Universe and Interesting Facts About the Moon.

How We Chose These

We looked for observatories that are famous for major discoveries, record-breaking telescopes, striking architecture or their role in public science. We mixed historic sites, which now welcome visitors, with working mountaintop observatories that lead modern astronomy. The list runs in order of when each one began work. Half of the ten sit more than 2,000 m above sea level, where the air is thin, dry and steady.

The 10 Famous Observatories at a Glance

No.	Observatory	Location	Began work	Best known for
1	Royal Observatory, Greenwich	London, UK	1676	The prime meridian
2	Jantar Mantar	Jaipur, India	1734	A 27 m stone sundial
3	Yerkes Observatory	Wisconsin, US	1897	A 40-inch lens telescope
4	Mount Wilson Observatory	California, US	1904	Hubble's galaxy discoveries
5	Griffith Observatory	Los Angeles, US	1935	Free public stargazing
6	Mauna Kea Observatories	Hawaii, US	1970	Twin 10 m Keck telescopes
7	Roque de los Muchachos	La Palma, Spain	1985	A 10.4 m mirror telescope
8	Paranal Observatory	Atacama Desert, Chile	1998	The Very Large Telescope
9	ALMA	Chajnantor plateau, Chile	2011	66 radio antennas
10	Vera C. Rubin Observatory	Cerro Pachón, Chile	2025	The largest digital camera

1. Greenwich Gave the World Its Prime Meridian

The Royal Observatory in Greenwich, south-east London, was founded by King Charles II in 1675 to improve navigation at sea.^[1] Its first building, designed by Christopher Wren, was finished in 1676, and John Flamsteed became the first Astronomer Royal. Today it is a museum on a hill above the River Thames.

Key Facts

Founded: 1675, by Charles II
First Astronomer Royal: John Flamsteed
Prime meridian: chosen at an international conference in 1884
Time ball: lowered every day since 1833 as a time signal for ships

Did You Know?

Longitude zero runs through the courtyard, and visitors can stand with one foot in the eastern hemisphere and one in the western. Greenwich Mean Time, measured here, became the basis for time zones around the world.

2. Jaipur's Jantar Mantar Has the Largest Stone Sundial

The Jantar Mantar in Jaipur, India, was built by Maharaja Sawai Jai Singh II and completed in 1734.^[2] It holds about 20 fixed instruments made of stone, brick and metal for tracking the Sun, Moon, planets and stars. UNESCO added it to the World Heritage List in 2010.

Key Facts

Completed: 1734
Builder: Sawai Jai Singh II, founder of Jaipur
Star instrument: the Vrihat Samrat Yantra, about 27 m tall
World Heritage: since 2010

Why It Matters

The great sundial's shadow moves about 6 cm every minute, letting local time be read to within a couple of seconds. Jai Singh built five such observatories across northern India, and the Jaipur site is the largest and best preserved.

3. Yerkes Observatory Holds a Record Lens Telescope

Yerkes Observatory, at Williams Bay in Wisconsin, was founded by the astronomer George Ellery Hale and paid for by the businessman Charles Yerkes.^[3] It was dedicated in 1897. Its main dome holds a telescope with a 40-inch (102 cm) lens, the largest refracting telescope ever used successfully for astronomy.

Key Facts

Dedicated: 1897
Main telescope: a 40-inch refractor
Nickname: the birthplace of modern astrophysics
Today: run by the Yerkes Future Foundation, open again since May 2022

Did You Know?

Lens telescopes much bigger than the Yerkes refractor are not practical, because a huge lens sags under its own weight and can only be held at its edge. After Yerkes, large telescopes switched to mirrors, which can be supported from behind.

4. Mount Wilson Showed That the Universe Is Expanding

Mount Wilson Observatory, in the San Gabriel Mountains above Los Angeles, was also founded by George Ellery Hale, with funding from the Carnegie Institution in 1904.^[4] Its 100-inch Hooker telescope, completed in 1917, was the largest in the world until 1949.

Key Facts

Founded: 1904
Hooker telescope: 100-inch (2.5 m) mirror, finished in 1917
Earlier giant: a 60-inch telescope, the largest working one in 1908
Solar towers: built in 1908 and 1912

Why It Matters

Using the Hooker telescope in the 1920s, Edwin Hubble showed that the Andromeda Nebula is a separate galaxy far beyond the Milky Way. He then found that distant galaxies are moving away from us, the first strong evidence that the universe is expanding.

5. Griffith Observatory Brings the Stars to Everyone

Griffith Observatory sits on Mount Hollywood above Los Angeles and opened to the public on 14 May 1935. The mining businessman Griffith J. Griffith left money for it, insisting that entry should always be free, and it still is. More than 13,000 people came in its first five days.

Key Facts

Opened: 14 May 1935
Admission: free, as Griffith's will required
Planetarium: the third to open in the United States
Famous visitors: Apollo astronauts trained in its planetarium in the 1960s

Did You Know?

Griffith Observatory has appeared in many films, most famously Rebel Without a Cause in 1955 and La La Land in 2016.^[5] Millions of people have peered through its main public telescope, a 12-inch Zeiss refractor.

6. Mauna Kea Is the World's Top Mountain for Telescopes

The Mauna Kea Observatories stand near the summit of a dormant volcano on Hawaii's Big Island, at about 4,207 m.^[6] Above much of the moisture in the air and far from city lights, the site has some of the clearest skies on Earth. Building began in 1967, and the first telescope saw first light in 1970.

Key Facts

Height: about 4,207 m above sea level
Science reserve: set up in 1967
Famous telescopes: the twin 10 m Keck telescopes and the Subaru telescope
Partners: research groups from about a dozen countries

Why It Matters

By total light-collecting area, no observatory site for optical and infrared work anywhere beats Mauna Kea. The mountain is also sacred to Native Hawaiians, and protests over new telescopes, especially the planned Thirty Meter Telescope, have made it a centre of debate about science and culture.

7. Roque de los Muchachos Hosts a Giant Mirror

The Roque de los Muchachos Observatory sits at about 2,396 m on La Palma, one of Spain's Canary Islands.^[7] At its formal opening on 29 June 1985, Spain's king and queen were joined by six other European heads of state. The island has strict laws to keep its night skies dark.

Key Facts

Opened: 29 June 1985
Height: about 2,396 m
Largest telescope: the Gran Telescopio Canarias, with a 10.4 m mirror
Other giants: the William Herschel Telescope, at work since 1987

Did You Know?

The Gran Telescopio Canarias, which began work in 2009, has the largest single-aperture optical telescope mirror in the world. Its mirror is made of 36 six-sided segments fitted together like a honeycomb.

8. Paranal's Very Large Telescope Lives Up to Its Name

Paranal Observatory stands on Cerro Paranal, a 2,635 m mountain in Chile's Atacama Desert, run by the European Southern Observatory.^[8] Its flagship, the Very Large Telescope, is made of four 8.2 m main telescopes that can work alone or be linked together to see finer detail.

Key Facts

Height: about 2,635 m
First main telescope: saw first light in 1998
Main mirrors: four, each 8.2 m across
Nearest town: Paposo, about 38 km away

Why It Matters

The Very Large Telescope helped track stars orbiting the giant black hole at the centre of the Milky Way, work that shared the 2020 Nobel Prize in Physics. The observatory's staff hotel, the Residencia, appeared in Quantum of Solace, a James Bond film from 2008.

9. ALMA Listens to the Cold Universe

ALMA, short for Atacama Large Millimeter/submillimeter Array, sits on the Chajnantor plateau in northern Chile at about 5,000 m.^[9] Its 66 high-precision dish antennas work together as one giant radio telescope, studying cold gas and dust where stars and planets are born. Its first images were released in October 2011.

Key Facts

Height: about 5,000 m
Antennas: 66, most of them 12 m across
Full operations: since March 2013
Partners: groups from Europe, East Asia and North America, hosted by Chile

Did You Know?

The antennas can be moved by giant transporter vehicles and spread up to 16 km apart, which works like a zoom lens for sharper views. ALMA also took part in the Event Horizon Telescope network that made the first image of a black hole in 2019.

10. Rubin Observatory Is Filming the Southern Sky

The Vera C. Rubin Observatory sits on Cerro Pachón in Chile and is named after Vera Rubin, who found strong evidence for dark matter.^[10] It released its first images in June 2025, and on the night of 29 June 2026 it officially began a ten-year survey known as the LSST.

Key Facts

First images: June 2025
Survey start: night of 29 June 2026
Camera: 3,200 megapixels, the largest digital camera in the world
Pace: a new image about every 40 seconds

Why It Matters

Rubin will photograph the whole southern sky every few nights, returning to each spot about 800 times in ten years. During early test surveys it found more than 11,000 new asteroids in about six weeks, and it is expected to find millions more.

Frequently Asked Questions

Why are most big observatories built on mountains?

High mountains sit above much of the water vapour and turbulence in the lower air, so starlight arrives sharper and less blurred. Remote peaks are also far from city lights, which would otherwise brighten the night sky.

Can the public visit these observatories?

Many can be visited. Greenwich, Jantar Mantar, Griffith and Yerkes welcome the public, and several mountaintop sites, including Paranal and Roque de los Muchachos, offer guided tours on set days.^[2]^[11]^[12]

Conclusion

From a stone sundial in Jaipur to a giant digital camera in the Chilean Andes, these ten observatories trace more than 350 years of looking up.^[13] Each one helped answer big questions about time, distance and the nature of the universe. For more on space, read the Finepedia guides Top 25 Interesting Facts About the Universe and Interesting Facts About the Moon.