Mount Equinox, in Manchester, VT, peaks at just 3,855ft of elevation. But unlike many mountains, you have to climb most of that to get to the summit. Prominence measures the elevation of the peak in relation to the land surrounding it, and is therefore a better metric for climbing in New England, where the summits are never really high enough for the altitude to play much of a role in fatigue and athletic performance. So while Equinox is only the 21st highest peak in New England, it ranks 7th in prominence, making it an excellent place to rack up a lot of vert in a relatively small number of miles.
This FKT route runs from the red gate up to the visitor's center at the peak via the blue trail, and back down the same way. Total time is gate to gate, and the runner must circle the visitor's center at the top before heading back down. The blue trail is wider at the bottom, but be advised it is single track higher up, and you'll want to avoid running it on a busy day. The views at the top are spectacular, so before or after your 5mi run I recommend taking time to soak it in.