Trsa is a name on a map more than a place with a centre, a scatter of houses above the long green reservoir that drowned the Piva canyon. Plužine is the nearest village of any size, a few kilometres up the water, and Žabljak sits on the Durmitor plateau beyond that. What you are really riding here is the shoreline road, and it is one of the odd ones in the Balkans: it clings to the canyon wall, ducks through short rough tunnels that look as if they were cut by people in a hurry, and opens out every few hundred metres onto water the colour of bottle glass.
The lake exists because of the Mratinje dam, finished in the 1970s, and it is a reminder of how much was given up for it. The Piva Monastery, a Serbian Orthodox house with a famous painted church, would have gone under, so the whole building was taken apart and rebuilt higher up near Plužine, with its frescoes cut from the walls and put back. If you have an hour, that is worth more than any viewpoint. The canyon itself is deep and narrow, limestone with pines and beech hanging on wherever they find a ledge, and in the early morning the water is still enough to double every cliff.
Ride it slowly. The surface is patchy, tunnels are unlit in places, and a rental bus coming the other way will not give you much room. Take the sunglasses off before the tunnels and put them back on after, which sounds trivial until you have done it badly once. Wind off the plateau can be sharp even in July, and in late autumn the shaded stretches hold ice well after the sun is up.
Do not count on fuel here. Plužine is a small place and Žabljak is only a bit larger, so treat the pump in Žabljak as the sure one and arrive with some in hand. Food is simple and good in this part of Montenegro: grilled meat, kajmak, bread still warm, and cheese from the mountain farms. Mobile signal comes and goes with the walls of the canyon, so sort out your route before you drop in.