Toward the end of the trailer, there's a shot of Lara entering a tomb, presumably for the purposes of raiding it. Forget what you know about the pokey caves and limited, small-scale platform-puzzling of the first game. This thing is huge, with a high-risk, high-ranging path clearly leading up to some kind of structure in the distance.
Expect the underground exploration in Rise of the Tomb Raider to be a much bigger deal, literally and figuratively. If the compartmentalised challenge tombs of the first game make a return, they'll very probably be scaled up. But it's very possible that the new game will start to move towards the territory of the original series, allowing the exploration of much bigger, more significant subterranean installations amid its presumed open-world environment.