grotto(n = noun.object) grot - a small cave (usually with attractive features);
is a kind of cave

   A natural covered opening in the earth; a cave; also, an artificial recess, cave, or cavernlike apartment. [1913 Webster]

grotto, n. (pl. -oes or -os)
1 a small picturesque cave.
2 an artificial ornamental cave, e.g. in a park or large garden.

Derivative:
grottoed adj.

Etymology:
It. grotta ult. f. L crypta f. Gk krupte CRYPT

N  receptacle, inclosure, recipient, receiver, reservatory, compartment, cell, cellule, follicle, hole, corner, niche, recess, nook, crypt, stall, pigeonhole, cove, oriel, cave, capsule, vesicle, cyst, pod, calyx, cancelli, utricle, bladder, pericarp, udder, stomach, paunch, venter, ventricle, crop, craw, maw, gizzard, breadbasket, mouth, pocket, pouch, fob, sheath, scabbard, socket, bag, sac, sack, saccule, wallet, cardcase, scrip, poke, knit, knapsack, haversack, sachel, satchel, reticule, budget, net, ditty bag, ditty box, housewife, hussif, saddlebags, portfolio, quiver, chest, box, coffer, caddy, case, casket, pyx, pix, caisson, desk, bureau, reliquary, trunk, portmanteau, band-box, valise, grip, grip sack, skippet, vasculum, boot, imperial, vache, cage, manger, rack, vessel, vase, bushel, barrel, canister, jar, pottle, basket, pannier, buck-basket, hopper, maund, creel, cran, crate, cradle, bassinet, wisket, whisket, jardiniere, corbeille, hamper, dosser, dorser, tray, hod, scuttle, utensil, brazier, cuspidor, spittoon, cistern, vat, caldron, barrel, cask, drum, puncheon, keg, rundlet, tun, butt, cag, firkin, kilderkin, carboy, amphora, bottle, jar, decanter, ewer, cruse, caraffe, crock, kit, canteen, flagon, demijohn, flask, flasket, stoup, noggin, vial, phial, cruet, caster, urn, epergne, salver, patella, tazza, patera, pig gin, big gin, tyg, nipperkin, pocket pistol, tub, bucket, pail, skeel, pot, tankard, jug, pitcher, mug, pipkin, galipot, gallipot, matrass, receiver, retort, alembic, bolthead, capsule, can, kettle, bowl, basin, jorum, punch bowl, cup, goblet, chalice, tumbler, glass, rummer, horn, saucepan, skillet, posnet, tureen, beaker, flask, Erlenmeyer flask, Florence flask, round-bottom flask, graduated cylinder, test tube, culture tube, pipette, Pasteur pipette, disposable pipette, syringe, vial, carboy, vacuum flask, Petri dish, microtiter tray, centrifuge tube, bail, beaker, billy, canakin, catch basin, catch drain, chatti, lota, mussuk, schooner, spider, terrine, toby, urceus, plate, platter, dish, trencher, calabash, porringer, potager, saucer, pan, crucible, glassware, tableware, vitrics, compote, gravy boat, creamer, sugar bowl, butter dish, mug, pitcher, punch bowl, chafing dish, shovel, trowel, spoon, spatula, ladle, dipper, tablespoon, watch glass, thimble, closet, commode, cupboard, cellaret, chiffonniere, locker, bin, bunker, buffet, press, clothespress, safe, sideboard, drawer, chest of drawers, chest on chest, highboy, lowboy, till, scrutoire, secretary, secretaire, davenport, bookcase, cabinet, canterbury, escritoire, etagere, vargueno, vitrine, chamber, apartment, room, cabin, office, court, hall, atrium, suite of rooms, apartment, flat, story, saloon, salon, parlor, by-room, cubicle, presence chamber, sitting room, best room, keeping room, drawing room, reception room, state room, gallery, cabinet, closet, pew, box, boudoir, adytum, sanctum, bedroom, dormitory, refectory, dining room, salle-a-manger, nursery, schoolroom, library, study, studio, billiard room, smoking room, den, stateroom, tablinum, tenement, bath room, bathroom, toilet, lavatory, powder room, john, jakes, necessary, loo, men's room, ladies' room, rest room, (uncleanness), 653 attic, loft, garret, cockloft, clerestory, cellar, vault, hold, cockpit, cubbyhole, cook house, entre-sol, mezzanine floor, ground floor, rez-de-chaussee, basement, kitchen, pantry, bawarchi-khana, scullery, offices, storeroom, lumber room, dairy, laundry, coach house, garage, hangar, outhouse, penthouse, lean-to, portico, porch, stoop, stope, veranda, patio, lanai, terrace, deck, lobby, court, courtyard, hall, vestibule, corridor, passage, breezeway, ante room, ante chamber, lounge, piazza, veranda, conservatory, greenhouse, bower, arbor, summerhouse, alcove, grotto, hermitage, lodging, bed, carriage, capsular, saccular, sacculated, recipient, ventricular, cystic, vascular, vesicular, cellular, camerated, locular, multilocular, polygastric, marsupial, siliquose, siliquous.

N  concavity, depression, dip, hollow, hollowness, indentation, intaglio, cavity, dent, dint, dimple, follicle, pit, sinus, alveolus, lacuna, excavation, strip mine, trough, honeycomb, cup, basin, crater, punch bowl, cell, socket, valley, vale, dale, dell, dingle, combe, bottom, slade, strath, glade, grove, glen, cave, cavern, cove, grot, grotto, alcove, cul-de- sac, gully, arch, bay, excavator, sapper, miner, honeycomb (sponge), depressed, alveolate, calathiform, cup-shaped, dishing, favaginous, faveolate, favose, scyphiform, scyphose, concave, hollow, stove in, retiring, retreating, cavernous, porous, infundibul, infundibular, infundibuliform, funnel shaped, bell shaped, campaniform, capsular, vaulted, arched.