A feature collection object contains an array of features, you gave it an array of geometries try
{
"type": "FeatureCollection",
"features": [
{
"type": "Feature",
"properties": {
"id": 1
},
"geometry": {
"type": "LineString",
"coordinates": [
[
-43.48283,
-23.02487
],
[
-43.48391,
-23.02475
],
[
-43.48233,
-23.02486
],
[
-43.48212,
-23.02443
],
[
-43.48243,
-23.02429
],
[
-43.48245,
-23.02477
]
]
}
},
{
"type": "Feature",
"properties": {
"id": 2
},
"geometry": {
"type": "LineString",
"coordinates": [
[
-46.65953,
-23.55865
],
[
-46.65953,
-23.5579
],
[
-46.65972,
-23.55809
],
[
-46.65941,
-23.55878
],
[
-46.65953,
-23.55896
],
[
-46.65903,
-23.55888
]
]
}
}
]
}
please forgive the product promotion, but if you'd like to skip administering the database you might consider trying Esri's cloud hosted feature service storage and open source Esri Leaflet plugin to write in the features.
afterward you can execute both SQL and spatial queries and specify GeoJSON as the output format.
here's a sample which incorporates the Draw plugin to sketch polygons
http://patrickarlt.github.io/uc-2014-esri-leaflet/demos/editing.html
you can create a free developer account at https://developers.arcgis.com to get 50 free credits a month to test out the tools. this gives you over 200MB of hosted feature service storage and individual queries against your data are free.
relevant links:
Esri Leaflet API Reference and examples
sample REST query
Disclosure: ArcGIS Hub / oss @ esri
Best Answer
You can try to use this tutorial from MapBox to get started.
You will need to create your own GeoJSON data for the stores and fountains that you want to display, and you can use this website to generate the GeoJSON file.