where exactly, can you point it out?
Here I have marked all the areas where it will be too thin for a player that has a 16 x 16 collision mask -
I also noticed a ton of tiling errors on the whole map that is either caused by incorrect sprites/tiles and mapping.
Please do not take that as a criticism, Im just trying to help because having tiling errors in your map would be VERY tricky to use in a game when it comes to collisions.
I take it youre using MS Paint to make your maps/tiles?
I used to use MS Paint for maps, but I got loads of errors too, so I found something else recently called graphicsgale.
I highly recommend you give it a try and become familiar with its tools.
MS Paint simply takes too long and can lead to errors unless you are extremely careful. Its too much hassle keeping on top of tiling errors.
Just my 2 cents anyway. Great work otherwise, my friend!!