The simplest, a quadrivia of the first kind, occurs when each street changes its name at the intersection. In Greensburg, Indiana, a quadrivia is formed by the intersections of SW 60, Park, Davis, and Ireland, found at N39°19.750 W085°29.342.
A quadrivia of the second kind involves a street split down the middle which has two names, and the cross streets changing names as well. This curious situation exists locally because Cincinnati and Norwood could not agree on a boundary street name. Cincinnati calls its half Rhode Island Avenue and Norwood calls its Section Road. At two intersections a quadrivia of the second kind occurs: Wayne in Norwood becomes Berkeley (N 39° 10.319 W 084° 27.560) and Worth in Norwood becomes Northcut in Cincinnati (N 39° 10.435 W 084° 27.552). Since it's theoretically possible that both the cross streets could have split names, such an intersection would also count.
Your task - find quadrivia. The roads must cross with at most a small jog, and be at the same elevation.
Clarification added 10/13/2008:
A small traffic circle at the intersection is acceptable, as long as it is unnamed.
"East" and "West" (or "North" and "South") streets with the same name (such as East Main and West Main, or North Center and South Center) do not qualify.
Clarification added 10/20/2008:
The signs must show the names of the roads themselves, not the names of the places where the roads lead.
Change made 6/24/2013:
A few people have requested to post a quintrivia - 5 streets with 5 different names. Since these are extremely rare, and wouldn't qualify for a category of their own, I have decided to allow them here. The rules:
1. The number of roads radiating from the center of the intersection must equal the number of different names. 4 roads with 4 names, 5 roads with 5 names, 6 roads with 6 names, etc.
2. Include the word Quintrivia, Hexrivia, Heptrivia, Octrivia, etc., in the Waymark name, if more than 4 roads/names are involved.
3. Include the names of all streets in the body of the description, since there are only four fields for listing them individually.
4. NO 3-WAY INTERSECTIONS!
5. Again, The number of DIFFERENT street names must EQUAL the number of roads at the intersection.