The best replacement for tunnels is bridges.

The best alternatives to tunnels are rated as following:
★★★★★  bridges
★★★  platform
★★★  skylights
★★★  plugs
★★  attack platform
★  solatube
★  attack platform starcraft

Your alternative for tunnels is not listed? Suggest!
Speaking about tunnels, one probably shouldn't forget about percy jones.

Other search terms related to tunnels and their ratings are:
★★★★★ percy jones
★ tents
ball pits
You have in mind a companion for tunnels and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of tunnels in all years. Click on graph for more.
tunnels
bridges
platform