This research uses a multi-scale spatial and discursive analysis to examine how a specific site informed colonial knowledge production in the 19th century Western Indian Ocean. With a focus on slave markets in Zanzibar and Muscat, I borrow from Lefebvre to situate these sites as dynamic spatial productions. Informed by new historiographies of East Africa, the Persian Gulf, and British abolitionism, we can approach slave market dynamics as grounded in the Western Indian Ocean world. Concomitantly, by focusing on how markets were represented and perceived by European observers, it is possibly to look at an array of imperial anxieties as unfolding spatially. This project, in this context, presents slave markets as spaces that were simultaneously produced by various ‘indigenous’ interregional actors, and by the European colonial imagination in an age of abolition and growing imperial ambitions. Reading 19th century British sources, I advance an argument for considering slave markets in Muscat and Zanzibar as spaces that not only illustrate an interconnected maritime arena, but also as important sites of colonial knowledge production that informed British imperial advances in the Persian Gulf and East Africa alike. Focusing on a series of first-hand accounts of the slave markets, together with parliamentary debates, newspaper articles, political diaries, and letters documenting the Western Indian Ocean slave trade, this project traces space as it unfolded in British antislavery rhetoric, particularly during the second half of the 19th century. The first section reads accounts of the market as telling of a transregional production of space where consumption, sociability, gender, performance, mobility, and power relations are displayed. The second and third sections explore how the slave market unfolded in the British imperial imagination in the context of a discursive and geopolitical shift associated with the re-imagination of Britain as an expanding, slave-less empire of free trade. I analyze how the slave market unfolded for visitors as a source of colonial knowledge production that evoked civilizational commentary. I then examine the ‘macro’ discursive level of parliamentary debates, newspaper articles and their associated images, public letters, and abolitionist publications to situate the slave market as a space of rhetorical relevance for abolitionism and imperial interests. In the concluding section, I locate this discursive production leading to the eventual prohibition of the slave market in 1873 as contributing to geopolitical shifts in the late 19th c. and to future conceptualizations of imperial relations.