In English you use the phrasal verb there+[to be] to mean something different than just an object being placed somewhere visible or known to the speaker and/or listener (i.e., there).
The same happens with Italian c'è and its corresponding plural and other tenses. In Spanish there is even a special "impersonal" conjugation of the verb haber —hay— for that meaning (even when in English one would use the plural form there are). Hay has very little use apart from this meaning, and no other verbs have such impersonal form, that I'm aware.
My gut feeling is that in Latin one should preferably use est, while exsistit and even ecce + esse (possibly elided) could be of some use in certain contexts.
My question is: Could you provide any examples, either Classical or from the Vulgate, that convey something like this meaning of there is in a natural way? I'm interested in both affirmative and interrogative sentences, and if there is any rule of thumb as for what (if anything) makes something different than est (ecce, exsistit) preferable. Any additional grammatical insights and/or partial answers are also welcome.
The next time you get into that dream, use a plain est. Here is an example from Caesar:
Flumen est Arar, quod per fines Haeduorum et Sequanorum in Rhodanum influit…
(Commentarii de bello Gallico I.12)
There is a river called the Saone, which flows through the territories of the Aedui and Sequani into the Rhone…
(W. A. McDevitte and W. S. Bohn, 1869)
For introducing simple things like this, the most idiomatic way I know is to use est. Using ecce gives emphasis, which is often unwanted. The point is to say "there is a river", not "lo and behold, a river".
For questions, you can use estne for "is there". Here is an example:
Estne adhuc aliquid mali in orbe mecum?
(Lucius Annaeus Seneca iunior, Hercules Oetaeus 1399–1400)
Is there still anything bad in the world with me?
(my quick translation)
There are also examples of estne with a dative of possession, but I guess those would not usually correspond to an English question with "is there".