Kotli: The Mill Village on the Mirna Headwaters

Kotli takes its name from kotao — the cauldron — for the pot-shaped hollows the river has drilled into the limestone bed where the cascades land. The Mirna here is young, running clear over shelves and steps, and every pool between the cascades is a piece of the same slow engineering. The village above the water was once the leading economic settlement of the Humština, the territory of nearby Hum: its millers ground the grain and its tailors cut the cloth, and their stable incomes built the larger, finer stone houses that still stand — roughly fifteen of them, preserved since at least the eighteenth century.

The village is formally protected as a rural monument complex and sits on the Glagolitic lane, the marked heritage route that threads central Istria's oldest inscriptions. It is also partly abandoned: several houses stand roofed but empty, the mill keeps its machinery, and the tavern by the pool opens for the season and closes after it. The result is a site that photographs as a museum and works as a swim hole — rare company for a free attraction.

Start at the village edge and walk down to the water: the first cascade empties into a natural pool the locals call Slap, broad enough to swim and shallow enough at its rim for children under watch. Below it the river steps down through the cauldron section, each hollow holding its own green basin, with low stone bridges crossing the channels between the mill and the houses. The preserved watermill stands at the heart of the row — machinery intact, wheel housing over the race — and its terrace is the site's best photograph.

Swimming here is lawful and long-established: the water runs warm and shallow in summer, and the pools renew themselves with every rain. Enter on the gravel margins, keep off the delicate moss edges of the cascades, and mind the slick stone around the mill race. Spring raises the flow and the noise; by August the pools warm to bath temperature and the cascades thin but keep moving — the Mirna's headwater springs rarely run dry entirely.

• Natural pool 'Slap' at the first cascade — the swim spot.
• Cauldron section: drilled hollows, each its own basin.
• Low stone bridges between the mill row and the houses.
• The preserved mill with intact machinery at the row's centre.

Hum, the walled hilltop town that markets itself as the world's smallest, lies about five minutes by road or twenty on foot from Kotli — its two lanes, the frescoed church and the rakija distillery make a tidy half-hour before or after the pools. The Glagolitic lane (Aleja glagoljaša) runs between Hum and Roč, marking the medieval script that this plateau preserved; Roč itself adds a defended town gate and a good lunch option when the Kotlić tavern is closed.

The driving logic works from either base: from the west coast (Rovinj, Poreč) count an hour to the Hum turn-off; from Buzet, twenty minutes south. Spring and autumn give the rivers their volume and the lanes their quiet; summer turns the pools into the day's destination and the villages into its cooling-off stops. Whatever the season, the circuit — Kotli, Hum, Roč — fits inside a half day with room for a long lunch.

• Hum: five minutes by road, twenty on foot — smallest-town marketing, real walls.
• Glagolitic lane: the marked heritage road between Hum and Roč.
• Roč: the lunch fallback when the Kotlić tavern is shut.
• From Buzet ~20 min; from the west coast ~1 h.