This is the top of the Green Gap Arch, East Dr. over a former bridle path around 63rd St. that's now part of the Central Park Zoo. It was built in 1861 and closed to the public (underneath) by 1934.
The 1861 Willowdell Arch is a few blocks north by 67th St.
The Bow Bridge crosses the southern part of "The Lake," seen looking east from West Drive. It was added as the park was being designed to provide a shortcut through the park's center.
One more arch for today, Glen Span carrying West Drive over "The Ravine" or "The Loch" (which drain "The Pool") near 102nd St. Inventive names here. This is the newest of all the bridges - 1865. Just a baby.
Here are some pedestrian signals along West Drive, heading south from Harlem. Because people have quick reaction times, they just get green and red, no bimodal "yellow" phase. (I'll note that yellow light is comprised of red and green light, so even though I think the birth of yellow as the center indication was a coincidence, it's very consistent.) The second assembly is a third vehicular signal tacked on top of a former 2-head signal assembly, which most certainly displayed only 2 indications to vehicular traffic in its lifetime.
Central Park's roadways were designed in the 19th century for carriages, and yet have held up surprisingly well into the 21st century. The roads open to vehicular travel are the West Dr./East Dr. loop around the park (with two cut-throughs) and a series of crossovers known as "transverses" that pass under both sides of the loop without any connection. Click for a video of the 85th Street Transverse, which actually takes 85th St. (WB) and 84th St. (EB) from the east side and turns them into 86th St. on the west side.
I'm saving the best for last, although it's the least photogenic of anything you might see in the park. It's a nondescript rock with an iron bolt stuck in it. Classy, Steve. Well, it's actually the oldest road-related find in all of New York City. This bolt represents the theoretical center of 6th Ave. and 65th St., if the two roads had been built instead of Central Park. It was hammered into the rock by John Randel, Jr. as he surveyed the streets of northern Manhattan in the 1810s. Because it has such a solid footing, it's the last confirmed survey bolt left in the city. Even if there are others hiding out, this is the only known one in the mapped but unbuilt grid of Central Park. Now ending on this scrap of iron is a little less weird, huh?