Article Detail Which is smallest planet ? Answer: Mercury Similar Questions : 1. Which is the Densest populated State of India ? Answer: West Bengal 2. Which is the lightest gas ? Answer: Hydrogen 3. Which is longest railway station ? Answer: Grand Central Terminal, Chicago(USA). 4. Which is Place of heaviest rainfall ? Answer: Mausinram (Meghalaya) 5. Where is largest Archipelago ? Answer: Indonesia 6. Which is Largest Dome in World ? Answer: St. Peter's Basilica (Rome) 7. Which is Longest road tunnel in the World ? Answer: Lærdal Tunnel (Norway - 24.51 kilometre) Read more from - Longest and Largest