On Dec. 31, 2010, we drove around the San Francisco Bay Area City Ring in 2 hrs, 14 min. The ring goes around the entire San Francisco Bay. I can't find that anyone has ever done this before, so we're the first.
We started in Palo Alto, drove north on Highway 101 to San Francisco, crossed the Golden Gate Bridge, went up to Napa, cut across the top of the Bay to Vallejo, came down through Berkeley and Oakland in the East Bay, and came around the bottom of the bay. It's 157.2 miles by my odometer.
What gave me the idea to do this? Beijing has six city rings. Chen Zhen did ring #2 in 13 minutes at 150 km/hr (95 mph), which earned him the nickname "Er Huan 13 Guy" ("13 Minutes on the 2nd Ring Road"). A motorcyclist did it in eight minutes at 315 km/hr (195 mph).
It may sound odd, but there are only a few city rings. There are city rings in the USA for Atlanta, St. Louis, Indiannapolis, Cincinnati, Columbus (Ohio), Washington, D.C., and Baltimore. That's it for the US as far as I can see.
Europe has a few. London has the M25 City Ring (120 miles, or 190 km.) The Berlin City Ring is the E56 (also 120 mile / 192 km.) Rome's City Ring A90 is both nearly perfectly round and it's 90km (56 miles). Moscow has three city rings.
You can use Google Maps to look for city rings.
If you know of more city rings, let me know.
And if you break my record, let me know.