In the context of the Indus Valley Civilization, Dholavira is primarily known for its expertise in water conservation techniques. This means that option 3 is the correct answer. Water was a vital resource for the people of the Indus Valley, and Dholavira stood out for its sophisticated systems of managing and conserving water. The city had an extensive network of reservoirs, canals, and water channels, which were used for irrigation, storing rainwater, and preventing floods. These water management strategies highlight the advanced engineering and urban planning skills of the inhabitants of Dholavira. While the other options, such as rock-cut architecture, seaport, and pottery, may have also been present in Dholavira to some extent, they are not its main claims to fame in the context of the Indus Valley Civilization.