•Microbotanical and micro-algae residues confirm early medieval turf walled structure.•Phytoliths reveal cereal cultivation at a Pictish fort.•Phytoliths and micro-algae provide important evidence for Pictish landscape use.•Microbotanical residues present where other organic remains are scarce. Early medieval architecture is notably difficult to trace in northern Britain. The fortuitous survival of an intact floor of a building located just outside a ringfort at Cairnmore, a high-status early medieval ringfort enclosure in Aberdeenshire, Northeast Scotland, allowed the targeted deployment of a paleoethnobotanical approach that utilized microbotanical (i.e., phytoliths) and micro-algae residues (e.g., diatom frustules) to illuminate the character of the unusual survival of an early medieval building in Scotland. This research revealed novel data on the architecture of the early medieval roundhouse floor in this poorly documented region and era for settlement remains, securely identifying the use of turf for walling in an early medieval lowland building. Evidence for roofing material was also preserved in the phytolith signature. Moreover, the microbotanical assemblage from Cairnmore was found to represent a use of a variety of ecological niches providing important evidence for landscape use. The presence (and absence) of particular microbotanical indicators also allowed interpretation of the possible uses of the structure. The results from this research demonstrate that microbotanical approaches can be critical in understanding architecture in regions where settlement survival is poor, highlighting the merits of microbotanical and micro-algae analyses in northern environments. The article concludes by advocating for the in-tandem assessment of these proxies in archaeological investigations where macrobotanical and other organic residues are poorly preserved.