Secret Places (3)
This is behind the bar on the second floor. There are two secret places shown in the snapshot. To find the first secret, press on the wine rack (right side of image). The second secret is behind an operable wooden panel further back in the bar (left side of image), which leads to the shark tank.
On the second floor, jump into the fountain (waterfall) by the swimming pool. You will be teleported to a secret area. Press the bloody handprint to open the last secret place. There's an Indiana Jones reference in this cave (be prepared to run).
"Check the vintage": Can be found on a wall in the secret shark tank area (nightvision goggles required). This is referring to the secret in the wine rack, as described in the secret place listing above.
"Behind the fountain": Written on a hallway wall on the second floor (nightvision goggles required). This refers to the fountain (waterfall) by the swimming pool on the second floor.
"Duke was here 2017": This message is hidden near the ceiling of the destroyed washroom stall. It is only intelligible after spacing the letters apart in the map editor. Incidentally, it won't be very long before we're actually in the year 2017!
Jump into the fountain (waterfall) by the swimming pool on the second floor. It will teleport you to the secret level area. Near the bloody handprint you'll find loads of trees and bushes. Use an explosive to clear them out. This secret nuke button warps to Freeway.