Prague Was Built to Cool Itself, and Then Forgot How

Every summer the conversation about overheated Czech cities restarts from the same place: shade sails, misting sprays, more trees, more air conditioning. A piece published by the architecture centre CAMP makes the less obvious argument — that Prague already contains a dense, working cooling system, built over six centuries, and that most of it predates the vocabulary we now use to describe it.

The passages

Prague holds one of the densest networks of covered passages in Central Europe, concentrated between Wenceslas Square and Národní třída. Platýz, Světozor, Černá růže and Lucerna are the names most people know. They arrived largely from the late nineteenth century onward as commercial infrastructure — a way to monetise the interior of a city block — but their thermal behaviour is the reason they are pleasant in August. A passage is a route through a block that never receives direct sun, buffered on both sides by heated mass, permanently in shadow and moving air.

Crucially, they connect. A passage is only climate infrastructure if you can cross the district through it, and in this part of Prague you largely can.

The arcades and the mass

The arcades of Malá Strana, around Malostranské náměstí and along Nerudova, are medieval and work on a different principle: not routing but thermal inertia. Masonry that thick absorbs heat slowly and releases it slowly, so the space beneath changes temperature hours behind the street. Combined with the shade of the arcade itself, the effect is a covered walk that stays usable through the worst of the afternoon.

Courtyards and gardens

Inside the blocks are the courtyards — Karolinum and Klementinum being the grandest examples — which perform the same trick vertically. A deep courtyard is a shaded reservoir of cooler air sitting inside a hot block, and the residential and semi-public versions of it are scattered across the whole historic city.

The baroque palace gardens climbing the Malá Strana slopes, Vrtbovská and Ledeburská among them, are the most deliberate version: vegetation and water used as architectural instruments rather than decoration, on terraced ground that moves air downhill.

What the new districts are doing about it

The argument's payoff is that this is not nostalgia. CAMP points to Masaryčka, Rohan City and Bubny-Zátory as projects consciously reintroducing the same two principles: blocks you can walk through rather than around, and public space that connects into a continuous network.

That is a low-technology answer to a problem usually discussed in high-technology terms. It is also a planning answer rather than a building one — permeability is decided at the level of the block layout, years before anyone designs a facade. Which is precisely why it is worth arguing about now, while the brownfields north of the centre are still drawings.