San Miguel is a small town and border crossing in the Putumayo department of southern Colombia.
This is an area that used to be very dangerous and most would not have considered a viable alternative to the Rumichaca border crossing near Ipiales. This appears to be changing and the area may be opening up for travelers. There is still some instability, but as of 2023 it seems relatively calm. Check the current situation before you go. Don't expect to see much jungle, however. Oil companies have moved in and appear to be rapidly laying waste to what little forest is left. Narco trafficking is also powerful in the region.
There is transportation from Puerto Asís (a couple hours), Villagarzón and Mocoa. Look for buses/camionetas that say "Puente Internacional".
You can cross the bridge into Ecuador on foot; both Ecuadorian and Colombian migration offices are on the Ecuadorian side of the bridge, in the same building. The actual border crossing is 3 km into Ecuador (both Colombian and Ecuadorian parts). There are colectivos from the bridge (there is some kind of bus terminal on the Ecuadorian side), or you can walk (not recommended on account of the excruciating heat/humidity).
You will be able to pay in pesos on the Ecuadorian side, and in dollars in the Colombian side.
The San Miguel river, briefly, as you cross the border.
Not much of anything.
There are several restaurants on the Ecuadorian side of the bridge
From Colombia, the towns of La Hormiga and La Dorada offer good and affordable hotels.
Lago Agrio : half an hour by bus.
Mocoa: 4 hours by bus.