Krier abandoned his architectural studies at the University of Stuttgart, Germany, in 1968, after only one year, to work in the office of architect James Stirling in London, UK.

These include the unrealized schemes for Kingston upon Hull (1977), Rome (1977), Luxembourg (1978) (which was his most comprehensive masterplan focusing on sprawl mitigation and town center repair), West Berlin (1977–83), Bremen (1978–1980), Stockholm (1981), Poing Nord, Munich (1983), a masterplan to be completed in the year 2000 for Washington D.C. (1984) commissioned by the Museum of Modern Art of New York; Atlantis, a neoclassical district for intellectuals and artists on Tenerife (1987);[12] Area Fiat, Novoli (Florence), Italy (1993), Corbeanca, Romania (2007), and the High Malton Masterplan for the Fitzwilliam Estate, Yorkshire, England (2014).

Krier has designed plans commissioned by public administrations, including the redevelopment of Tor Bella Monaca, a degraded suburb of Rome (2010), and a long-term redevelopment policy plan for the municipal area of Cattolica, Rimini, Italy (2017);[13][14] he was able to apply similar principles to build developments such as Knokke, Heulebrug, Belgium (1998), completed without his direction; and in his masterplan for Newquay growth area (2002–2006), Cornwall, UK, continued after his resignation by Adam Associates.

The measurements and geometric organization of a city and of its quarters are not the result of mere chance or accident or simply of economic necessity, but rather represents a civilizing order which is not only aesthetic and technical but also legislative and ethical.

[16] In response to this, Krier proposed the reconstruction of the European city, based on polycentric settlement models which are dictated not by machine scale but by human scale both horizontally and vertically, of self-sufficient mixed use quarters not exceeding 33 hectares (82 acres) (able to be crossed in 10 minutes walk) of building heights of 3 to 5 floors or 100 steps (able to be walked up comfortably) and which are limited not by mere administrative borders but by walkable, ridable, drivable boulevards, tracks, park ways.

Krier has written a number of essays − many first published in the journal Architectural Design, against modernist town planning and its principle of dividing up the city into a system of single use zones (housing, shopping, industry, leisure, etc.

Indeed, Krier sees the modernist planner as a tyrannical figure that imposes detrimental megastructural scale more dictated by ideology than necessity.

The principle behind Krier's writings has been to explain the rational foundations of architecture and the city, stating that “In the language of symbols, there can exist no misunderstanding”.

That is to say, for Krier, buildings have a rational order and type: a house, a palace, a temple, a campanile, a church; but also a roof, a column, a window, etc., what he terms “nameable objects”.