I have a question about our epic ,Ramayana .It was said that Lord Srirama built a bridge between India and Sri Lanka with the help of his vanara senna ,if so where is that bridge ?
The following issues are to be noted for understanding the reasons for non-existence of bridge constructed by Sri Rama, now.
The distance between the land from where Sri Hanuman flew towards Lanka of Ravana was 100 Yojanas,ie., nearly 1300 Kms.
Ravana's Lanka was not present day Sri Lanka.
As per the Ocean God's assurance to Sri Rama, the bridge got constructed by Sri Rama would collapse after the to and fro journey of Sri Rama and his army towards Lanka.
विधास्ये येन गन्तासि विषहिष्ये ह्यहम् तथा | न ग्राहा विधमिष्यन्ति यावत्सेना तरिष्यति || २-२२-२८ हरीणाम् तरणे राम करिष्यामि यथास्थलम् |
"O, Rama! I shall make it possible to see that you are able to cross over. I will arrange a place for the monkeys to cross me and bear with it. As far as the army crosses me, the crocodiles will not be aggressive to them."
अयम् सौम्य नलो नाम तनुजो विश्व कर्मणः | पित्रा दत्त वरः श्रीमान् प्रतिमो विश्व कर्मणः || २-२२-४४
"O, excellent man! This one, named Nala, a glorious person, is the son of Vishvakarma; who was given a boon by his father and is equal to Visvakarma."
एष सेतुम् महाउत्साहः करोतु मयि वानरः | तम् अहम् धारयिष्यामि तथा हि एष यथा पिता || २-२२-४५
"Let this greatly energetic monkey build a bridge across me. I can hold that bridge. He is just the same as his father."
So the bridge got constructed by Sri Rama would be in place, as long as He and his army pass over it, ie., it will remain intact for their to and fro journeys. There after it will collapse.
Sri Rama performed the return journey by Pushpaka Vimana and hence the bridge would have been collapsed immediately thereafter.