There is to introduce a new piece of information which is in most cases, I believe, followed by the indefinite article. So I suppose this sentence is wrong, no?
There is the town hall on the left corner and a gym on the right corner.
No, it's actually quite possible - if comparatively rare - to have 'there is/are' followed by a definite noun phrase. It tends to occur, however, in just this type of situation, where reference is to some geographical or topographical feature.
1) There once lived in Greece a very wise man.
2) There stands a church on the hill.
3) There began a long and ~ battle.
4)* There ended a long and ~ battle.
#4 is perfectly well-formed, if a little literary.
#5 is so unidiomatic as to be effectively unacceptable on account of the combination of preposed adverbial (there) and verb 'end' with a spatial reference.