My dad wanted a tunnel for our Lionel Train Set, so I designed one in Blender! Video demo is here: https://www.youtube.com/watch?v=O_qTKXkKmnA&feature=youtu.be This tunnel is 224mm wide, 290mm long, and 140mm tall. It is split into two pieces, both of which require the entire build volume of the MakerBot Replicator Dual! It has a guaranteed clearance height of 110mm and width of 90mm, plus a curved ceiling which adds up to 20mm additional clearance height depending on the object traveling under it. The platform above can completely fit an object with a blueprint of 160mm x 210mm, but actually has more room due to the mountainous structure. The tunnel also has a 70mm diameter hole at the top in case you need to fit a plug to power any decorations on top.Print both pieces of the tunnel***.Print settings are up to you, but this is what I did: MakerBot Desktop PLA LOW Resolution (Fastest) print settings, except with 5% infill: Layer Height: 0.3mm Shells: 2 Infill: 5% Support: YES Rafts: NO (I also like to keep my build plate at 40C) Build time was around 13.5 hours for each piece. Even though MakerBot Desktop projected needing almost 2 lbs of filament, it seems the actual print required less, seeing how my 2lb filament spool has 15-20% plastic left. I created two holes that can be fitted with pins to join the tunnel, but I think using glue may be easier. ***I added "no holes" versions of the two tunnel pieces. These versions don't have cylindrical holes on the inside walls. I had originally put those holes there to allow for connecting using pins, but removing these holes may allow you to use 0% infill to save on plastic. Then, simply glue the pieces together using a crazy glue or Loctite super glue (or anything else that is good at bonding your plastic together)