What the Savage Land is
Stan Lee and Jack Kirby introduced the Savage Land in X-Men #10 (March 1965). The hidden tropical jungle in Antarctica has surviving dinosaurs, prehistoric humans, and the time-displaced wild man Ka-Zar. The setting has been a recurring Marvel location across decades.
Collector context
X-Men #10 trades in the four-figure range at CGC 9.4 and above.