You could focus on the general organization of the building, on one of its constituting elements, on its typology, function, or ruling principles, on its relationship with the city, on the specific use of history, etc.
To support and enrich your argument, you might also refer to other buildings too.

(Example: you want to compare the architectural order in Alberti’s Rucellai Palace vis-à-vis Brunelleschi’s Foundling Hospital. You could use Rudolf Wittkower’s text to explain their specific use of arches, columns, entablatures, and walls, and you can enrich the argument mentioning their common reference but different use of the Roman Coliseum and Tabularium).

Support your argument with:
2 re-drawn plans (not merely copy-pasted from internet) emphasizing specific aspects of the building;
2 schemes (axon, exploded drawing, facade detail, geometric organization, modules, etc.) necessary to better explain your argument;
4 images carefully chosen.
Footnotes Required