The Marq museum has the double quality of being located strategically in Buenos Aires city together with an iconic presence. It’s 19th century railway architecture provides the building a strong identity. Our proposal for the new museum extension took this account, focussing in the dialog between both buildings. We opposed the old vertical tectonic nature of the existing museum to a new metallic, light and vaulted extension. Evoking Retiro’s terminal domes. Both buildings belong to different worlds and ages.They engage, yet don’t touch, increasing the tension that unifies them.