Warehousing and distribution tend to be the most labour-intensive component of logistics. Moreover, these have become more important with the explosion of online purchases, especially with expedient shipping. Recently, significant advances in aisle designs for unit-load, that is, single-pick, warehouses have achieved up to a 20% reduction in the expected travel distance. However, the effectiveness of these designs for general order-picking has been little investigated. The research herein addresses this by thorough examination of optimal designs that embrace a wide range of possibilities considering different order picking characteristics. The results suggest that the historic practices of orthogonal pick and cross aisles perform surprisingly well for a wide variety of order picking environments especially those with longer pick lists. The benefits of alternative designs over traditional configurations are modest with improvements of less than 5%. However, our extensive experimentation and analysis show a potentially useful new design schema that emulates the Karlsruhe, or Moscow, radial motif. This appears repeatedly and places the depot, counter-intuitively, at the centre of the long side, rather than where the cross aisles meet. Furthermore, it is very different from conventional orthogonal aisles. The findings are synthesised into a straightforward concise set of design rules for practitioners.