All twenty-four entries

The plateau is bounded and divided by ranges, and the passes between them decided every route across it.

The major rivers of Asia rise here, and the inhabited valleys are the low warm exceptions to a cold high surface.

The northern plateau is a basin with no outlet, so its lakes are salt and its water goes nowhere.

Barley ripens higher than any other cereal, and the altitude at which it stops is the altitude at which settled farming stops.

Roasted barley flour keeps, needs no cooking and can be eaten anywhere, which is why it is the staple rather than bread.

Transport, wool, milk, hair for tents and dung for fuel in a place with no wood — the whole economy rests on one animal.

Woven from yak hair, the cloth swells when wet and closes its own weave, so a loose fabric becomes a rainproof roof.

Salt from the northern lakes moved south and grain moved back, on the backs of the same animals.

Damp earth compacted in shuttered lifts makes a wall that is cheap, thick, and warm in a place where fuel is scarce.

Walls that lean inward as they rise are more stable and shed weather better, and the batter is the single most recognisable thing about the architecture.

Flat roofs work where it barely rains, and timber is rare enough that beams are reused across generations of building.

The fortified building on a spur is a building type, sited for command of a valley rather than for comfort.

Ground azurite, malachite, cinnabar and orpiment, bound in animal glue — the colours are stones before they are paint.

A painted figure is set out on a ruled proportional grid before any colour is laid, so the drawing is a measurement rather than a sketch.

Backstrap and frame looms produce narrow cloth that is joined in strips, which is why the patterning runs the way it does.

Text was printed from carved blocks onto long loose leaves, one block to a page, and the blocks were kept.

The writing system was devised in the seventh century under Songtsen Gampo, traditionally credited to Thonmi Sambhota, and was built for a language it fitted better then than now.

A sealed chamber held tens of thousands of manuscripts, and the Tibetan among them preserves a period almost nothing else survives from.

The language of those documents differs from the modern written form in spelling and grammar, which is how the manuscripts are dated.

Paper made from a toxic shrub root resists insects, which is a large part of why so much survived.

The Survey of India trained Indian surveyors to cross the plateau on foot and measure it while they walked, because they were forbidden to be there.

He walked measured paces counted on a rosary shortened to a hundred beads, and hid his notes inside a prayer wheel.

A sextant, a boiling-point thermometer and a compass are enough to fix a position and an altitude if you are patient.

Water boils lower as you climb, so a thermometer becomes an altimeter and a route becomes a profile.