Höhlenforschung

If Spelunking would enter the battlefield at the same time a land you control would enter the battlefield tapped, that land still enters the battlefield tapped.

If a land has an ability that says it enters the battlefield tapped, you choose the order in which that ability's effect and Spelunking's effect apply. This means you can choose to have the land enter tapped or untapped. If a land you control is simply put onto the battlefield tapped without a replacement effect being applied, it always enters untapped if you control Spelunking.