The apt is very close to San Marcos's square but it was very difficult for us to find the apt. We tried Google maps and the instructions on the paper but we kept going in circles until we called them and got exact instructions. Apparently, this is the case for most apts in Venice so my experience may not be unique. Other than that, the apt was clean and comfy. You first have to check into the office and then take the ferry over to San Marcos.