Entry No. 68 — the Chicago file — filed under: roadside-oddity
Yerkes Observatory
Called the birthplace of modern astrophysics, this 1897 lakeside observatory houses the largest refracting telescope ever used for science: a 63-foot, 12,000-pound instrument with 40-inch lenses, so finely balanced it can be swung by hand. Einstein visited, and Edwin Hubble and Carl Sagan worked here. The University of Chicago handed it to a local foundation in 2020, and after restoration it reopened for daytime tours and night-sky telescope sessions on its Olmsted-designed grounds.
The story
When Chicago streetcar tycoon Charles Tyson Yerkes needed to buy back a little public reputation after serving time for larceny, astrophysicist George Ellery Hale knew exactly how to play him. He convinced Yerkes to fund a grand facility anchored by a 63-foot, 12,000-pound refractor with 40-inch glass lenses—the physical upper limit before glass warps under its own weight. Architect Henry Ives Cobb wrapped the observatory in Beaux-Arts and Romanesque detail, sneaking satirical stone caricatures and gargoyles into the columns, while the telescope itself was shown off at the 1893 World's Columbian Exposition in Chicago before installation in 1897.
This became the literal birthplace of modern astrophysics. Edwin Hubble completed his graduate research in these rooms, Nancy Grace Roman earned her doctorate studying galaxy spectra here, Carl Sagan worked the floor, and Albert Einstein dropped by in 1921. To reach the telescope's eyepiece at varying angles, Cobb engineered an entire indoor floor that functions as a 75-foot rising elevator. The University of Chicago walked away from the site in 2018, but a local foundation acquired it in 2020, spending millions to clean the rotunda marble and restore the 50-plus acres of Olmsted-designed grounds.
What it's like
Pulling onto the 50-acre lakeside grounds feels like entering a private estate, but you won't be wandering inside on your own terms. Unescorted visitors aren't permitted in the building, so you'll wait outside until a staff member opens the south doors 15 minutes before your ticketed tour. If you score a night-sky session, dress significantly warmer than you think you need to—the giant dome stays unheated to match the outdoor air temperature and prevent thermal distortion. Standing under the dark dome while the massive floor rises beneath you and the 12,000-pound scope glides by hand power is unforgettable, but night tickets sell out weeks early online.
The move: Book a night-sky tour, stand under the great hand-balanced refractor, then take turns at the eyepiece on a clear evening over the lake.
📍 Before you go Tours run select days (typically Tue/Fri/Sat) and require advance tickets; night sky tours sell out. About 80 miles northwest of Chicago near Lake Geneva.
- 📍 Williams Bay, WI
- 💸 $
- ⚡ Up for anything
- 🌗 Indoors
Where: 373 W Geneva St, Williams Bay, WI 53191
Hours: Added 2026-06-23 — confirm current hours before you go.
⚠ Seasonal or scheduled — always check before you go.
Pair it with
- Dearborn Observatory (Northwestern University) — Follow one 19th-century astronomical powerhouse with another by comparing Yerkes' 40-inch refractor to Evanston's historic 18.5-inch lens.
- Cernan Earth and Space Center — Continue your stargazing itinerary on the drive back toward Chicago with a planetarium show named after the last astronaut to walk on the moon.
- Volo Museum — Break up the drive to Williams Bay with 35 acres of bizarre mechanical oddities, antique cars, and pop-culture artifacts.
- Sanfilippo Place de la Musique — Pair one hyper-engineered late-19th-century marvel with another by visiting this nearby private estate filled with restored automated orchestrions.
Good to know
Can I walk inside Yerkes Observatory without a tour ticket?
No. The building is only accessible via scheduled guided tours and special events. The surrounding Olmsted-designed grounds, however, are free and open to walk from dawn to dusk.
How do I get tickets for night-sky telescope viewing?
You must reserve tickets in advance on the official Yerkes Observatory website. Night sessions have strict capacity limits and routinely sell out well ahead of time.
Where is Yerkes Observatory located relative to Chicago?
It is in Williams Bay, Wisconsin, on Geneva Lake—approximately 80 miles northwest of downtown Chicago, or about a 90-minute drive.
Why is the Great Refractor telescope famous?
It is the largest operating refracting telescope ever used for scientific research, featuring a 63-foot tube and 40-inch glass objective lenses.
Plan a visit & invite your people →
Further reading: Wikipedia · Official site · nationalgeographic.com · wi101.wisc.edu · olmsted.org
last checked: 2026-06-23