To get Classic Lost Valley in Sonic Speed Simulator, you generally need to unlock another Secret Zone first, reach 150 Team Mastery , and then buy the entrance for 50,000,000 in Lost Valley. It also has a minimum level requirement of 30 and can be reached through a portal hidden behind a patch of falling sand near spawn in Green Hill.

What to do

  1. Unlock any other Secret Zone first.
  1. Raise your Team Mastery to 150.
  1. Have 50,000,000 currency ready in Lost Valley.
  1. Go to Green Hill and find the hidden portal behind the falling sand patch on the left side near the closest loop to spawn.
  1. Make sure your character is at least level 30.

Quick note

Older guides and videos mention different steps, like finishing quests or time trials, but the newer wiki entry says the current unlock for Lost Valley Classic is the Secret Zone requirement, Team Mastery, and the 50,000,000 purchase.

Mini guide

If you are stuck, the fastest practical checklist is:

  • Reach level 30.
  • Unlock one other Secret Zone.
  • Grind Team Mastery to 150.
  • Save 50,000,000.
  • Find the sand-covered hidden portal in Green Hill.

TL;DR: Unlock another Secret Zone, hit 150 Team Mastery, gather 50,000,000, and enter the hidden portal in Green Hill.