Looks like an appearance of Main Street. The cars are now more agressive, forming a slippy road in vertical and horizontal forms. There are 2 paths (switching paths every round). The bloons on the first path (vertically) starts at the top-left corner, while the bloons on the second path (horizontally) starts at the bottom-left corner. You can build towers on the giant road, not on the bloons' paths. No water.